I left Plusnet mobile in December however the final bill, although only for a few days, charged the full month. 3 weeks later I received the refund of £9.03, that was on 21st January. Now, on 1st March, £9.03 has been taken from my account! That's the refund amount clawed back. Apparently a system error. I have to wait until 3rd or 4th March for it to appear on Plusnet account and then a further refund of £9.03 will be issued which with take 10 days. What billing system do you have?