Their tone of voice ranges from sheer anger to utter despair. Some are desperate, others confused. But those calling homelessness charity Shelter have one thing that unites them – they’re fast running out of options.

Over the past year alone, calls to the organisation’s helpline – which offers legal housing advice – have increased by 25%, rising to more than 618,000.

HuffPost UK spent a day at a centre handling desperate calls from people facing eviction, homelessness or living in unsafe properties.

Christmas is an especially busy time. During the festive period last year, someone made a call for help every 22 seconds. More than 500 calls were made on Christmas Eve and Christmas Day.

This winter is no different, with thousands of desperate people reaching out for advice.

Among them is Sarah*, a mother-of-three. After being made homeless 13 times, she and her young children are set to spend this Christmas in a B&B.

Stuck in a single room where it’s likely they will all have to sleep in the same bed, they won’t have a kitchen of their own to cook Christmas dinner, or a bathroom that is not shared with strangers.

But Sarah is not what you might expect when you think of a woman trapped in such dire circumstances.

A working parent who is training to become a teacher, she is one of the growing number of middle class people battling homelessness.

According to Shelter, sky-rocketing rents and short tenancies – combined with a lack of social housing to fall back on – mean that Brits from all walks of life are now at risk.

“In recent years, we have seen an influx of calls from what the media called the ‘squeezed middle’, helpline operations manager Andrea Deakin told HuffPost UK from the floor of a Sheffield call centre.

“These are people who are earning reasonably good salaries, but because rents get so high where they live, they can’t afford to stay there.

“Then, when they have to move, moving costs and a deposit are so great that they find themselves unable to afford somewhere else.”

A lack of social housing means that a family with a legal right to be re-homed will often find themselves placed back into private accomodation by the council, Deakin said, trapping them in an “impossible” cycle.

“The housing market today is really not fit for purpose,” she added. “There’s more demand for our service than ever before.”

Helpline adviser Mark Cook continued: “When I first started working here in 2010, there was a certain kind of caller who might have rang.

“Over the course of the last seven years, it’s become literally any kind of person, from any background, on any pay.”

He added: “One tiny economic shock can send people completely adrift. We are now looking at the pounds, rather than the tens of pounds.”

During a trip to one of the charity’s hubs, HuffPost UK learned about three cases that illustrate Britain’s current housing crisis – and why services like the helpline are so critically important.

The full-time carer facing eviction over £365

While visiting the centre, HuffPost UK listened in to some of the calls advisors deal with everyday.

During one call, a man named Dave* – a full-time carer for his autistic adult son – described how the pair are facing homelessness this Christmas after being threatened with eviction from their home of 15 years.

His voice hoarse with emotion, he explained how the housing association which owns his flat has started asking for rent in advance.

As a result, Dave – who receives his housing benefit a month in arrears – has found himself owing £365 and is subsequently facing possession action.

“It feels as if they are using a sledge-hammer to crack a nut,” he said.

“They are a huge organisation – what is my £200 or £300 going to do for them? It’s only one month, you think they could be understanding.”

Dave, who suffers from depression, added: “This has sent by anxiety through the roof. It’s coming up to Christmas and I just can’t deal with this.”

Taking Shelter’s advice to pay a couple of extra pounds a week in rent in an attempt to appease the housing association, he admitted he had considered taking out a high-interest pay-day loan to cover the costs before speaking to Shelter.

“It’s been so nice to speak to someone about this,” he said. “I can’t thank you enough.”

The children made homeless 13 times

Andrea Deakin, helpline operations manager at Shelter, described one recent case which had resonated with her.

“Just this week, we spoke to a woman who has three children,” she said. “She works and is training to become a teacher, but has been made homeless 13 times thanks to short-term leases and landlords putting the rent up.”

Stuck in a “dreadful cycle” where her already restricted funds are drained by moving costs, the trainee teacher is once again stuck living in a B&B with her young children.

“It’s had a huge emotional impact on the kids – they are currently receiving counselling,” said Deakin.

“There’s damp in the temporary property, so there’s also been a physical effect on the kids when it comes to things like asthma and chest infections.

“And then there’s the logistics of four people – three of them children – living in one room in a B&B where they have shared bathroom facilities and a shared kitchen.

“Small children often don’t want to go to the loo or have a bath in a space that is shared with other people. ”

She continued: “As a parent, you don’t want to think you can’t provide for your children.

“But she’s a working woman who is training to be a teacher – no-one can say this should be happening.

“In reality, most of us are now only about three pay cheques away from being in that situation ourselves.”

The family trapped in a ‘falling down’ house by ‘immoral’ council

During another call to the centre, a mother-of-two named Jill* described how her family have effectively been trapped in their subsiding house by the council’s “immoral” demands that she lie to unsuspecting tenants about the damage.

The 30-something told Shelter how her current home is not only “falling down”, but that a lack of bedrooms means her autistic son is currently forced to share with his two-year-old sister – an “awful situation” that is “impossible in the long-term”.

The family’s only chance of being rehoused in the next seven years is through a “swap” with other council tenants, Jill said.

But with the council only agreeing to carry out cosmetic work on the subsiding property, she was told by a council surveyor she should lie to any potential tenants about the structural damage.

Otherwise, no-one else would take on the property, he said, leaving her family trapped there.

“They are holding me to ransom,” Jill told the call handler, who described the situation as “horrifying”.

“It feels like they are saying: ‘Either you’re going to lie, or we are not going to do what you want us to.’

“I could not lie to someone else about this – I would be devastated if I thought I had found my dream home and in reality it was falling down,” she said.

“I pay full rent and council tax and I don’t get any kind of benefits – I’m not going to stand for being screwed over.”

But while the Shelter adviser agreed that the situation is “morally wrong”, he was forced to explain to Jill that the council are acting inside the law, as long as the damage does not pose a threat to tenants.

“It’s a truly shocking case,” he said.

How to help  Through its helpline, website and face-to-face advice, Shelter helped more than five million people dealing with housing issues or homelessness in 2016.  To donate, visit shelter.org.uk.