A Hackney Homes phone survey came under urgent review by the council after the Gazette flagged up that some people replying to it were being charged at international rates.

The number appeared to be from the UK, and looked as though it would be free for most people with mobile phone packages to respond to.

But in fact the 07 prefix meant it was registered in Guernsey and some mobile phone networks were charging up to 25 pence to Hackney Homes tenants who replied.

The matter was brought to the Gazette’s attention by Dave Spice, aka DJ Spice, a resident of St John’s Estate, Hoxton, who was worried other residents might be caught out by they hefty charges. He was sent the text asking him how satisfied he was with the repair a Hackney Homes technician had just carried out to his boiler.

He tried to respond to say he was very satisfied with his repair, but when the text would not send he realised it was because international calls are barred on his mobile.

When the Gazette contacted the council they immediately reviewed the service and made sure it was no longer provided by an overseas service provider.

Nick Jeffreys, business development director, from the SMS provider Cloud Dialog which runs the service for the council said they had not been able to establish definitively how long the high charges had been going on for, or how many people could have been affected by it.

Out of the 120,000 repairs carried out by Hackney Homes each year, the text survey is sent to about 15,000 residents, of whom on average 4,200 reply.

Mr Jeffreys said: “We always provided the numbers on the basis they are ordinary UK mobile numbers and there’s no element of add-on cost to the text if you reply to it.

“When Hackney made us aware of this we went to the people who provide us with the numbers, it transpired the numbers were registered in Guernsey.”

He continued: “The problem we have is everyone is being very evasive, it looks like one of the big mobile networks has found a wrinkle in the small print and decided they can reclassify what everyone else would see as a UK code and hit their customers with an excess charge and we’ve all fallen down that hole because none of us knew it had happened.

“I think it’s important to understand that from Hackney’s point of view they are spending money on a service which is aimed to find out if customers are happy, no one is trying to make money out of this anywhere.”

Mr Jeffreys believes the change could have taken place two months ago, and made sure that four hours after the council told them about the glitch, the Guernsey number was changed.

A Hackney Homes spokesman said they were grateful to the resident for bringing the matter to their notice.