England ScottishPower owe me money

This happened years ago when SP messed up our bill considerably. So I left and agreed to pay it off at a minimal amount. For context it was entirely their mistake and after agreeing to repay I found that I could have just legally not paid.

Just as the repayment finished, they did not cancel the repayments, and I spent the next 2 years fighting for my life, a lot of time in hospital and am now disabled and immune compromised.

So I over-repaid 2 years worth. First they say they can not issue me a refund into my bank. I don't leave the house so can't deposit a cheque (even if banks existed anymore). They agreed. But said they need to do something with my account first at their end which they have not done as I can see money still coming out of my account. That's about 2 months ago now.

As of today,

1. they never stopped taking money from my account and it continues.
2. Have not communicated in almost 2 months.
3. The amount is about £1000

What do I do next? I've had a gut full of their lies, excuses and need advice before I explode at them.

Thanks and apologies for the rant