We were charged for someone else's electricity usage

We moved to the UK and switched to Good Energy mainly based on its "green" profile. This was a big mistake and I'm sure our experience couldn't have been worse.. First of all, it took over a month for them to switch from the supplier and when they finally did, they were charging £50/month by direct debit even without explaining what it was based on. However, we were simultaneously using the British Gas meter and topping it up on a regular basis. The whole system seemed very messy and we started wondering what they were charging us for. Since we are not from the UK, we didn't know how this works here and we thought that Good Energy is supplying us only electricity, while we're paying for the gas to British Gas. When I started investigating this, it took them a long while to realise that we had actually been paying for our NEIGHBOUR'S electricity! They just told that they had made a mistake and were charging based on a wrong meter. How is that even possible? They never confirmed the number of the meter with us. Altogether, we paid £150 to this company and still haven't gotten our money back. This is what they say: "Unfortunately, we have to wait for your previous provider to officially accept the erroneous transfer of the supply before we can refund any payments made, and this has caused the delay." We would NEVER recommend this company to anyone!!! Stay far from it, please.