I received around 10 texts from my mobile phone provider, Three, saying things like “Oops, we can’t process your request at the moment due to a systems issue” with a link to click on.

I was wary, given that I hadn’t contacted Three, and tried to call customer services but got a pre-recorded message saying it was unavailable. Two days later, I realised my phone had been disconnected.

I checked my bank account and found payments of more than £1,000 had been made to an online money-transfer service which I did not recognise.

I have since been trying to get answers from Three. I was promised a replacement sim card which hasn’t arrived and, a week on, I’m still without a phone service. To add insult to injury, my direct debit for my disconnected phone contract went out of my account this morning.

It seems to me that although phones are routinely used for banking purposes, service providers are ill equipped to deal with fraud compared to banks.

JC, London

It seems that a fraudster stole your number by using your identity to request a porting authorisation code (PAC) to transfer it to their own sim card. Your line was disconnected when the transfer was complete.

This is known as “sim-swap fraud” and it enables scammers to receive all calls and texts intended for you, including one-time authorisation codes for bank transactions. Often they can glean information to pass security questions from a customer’s social media sites.

Speed is of the essence if you find you’ve been defrauded, so it was unacceptable that you were unable to contact Three. The company admits that its helplines were not running at full capacity due to the pandemic, and that it could have been more helpful.

Your line has been restored and the charges refunded for the time you were without a service, but you will have to grapple with your bank to see if you can get the £1,000 refunded.

Three says: “We have introduced a number of enhanced checks for anyone attempting to access someone else’s phone number, and are working in close collaboration with the rest of the telecoms industry to monitor, identify threats and take action.”

If you need help email Anna Tims at your.problems@observer.co.uk. Include an address and phone number. Submission and publication are subject to our terms and conditions