ICB Swapping from personal budget to managed budget

so about 3 years ago I swapped over from a personal budget to a managed one. I sent the ICB all the relevant paperwork and its all worked out smoothly since then. The trouble is the ICB still continued to send me money for personal payments even tho I was moved to a managed budget. I have emailed them on numerous occasions and the payments stopped about 12 months ago. There is still £26 thousand pounds in the account that’s just sat there. I have emailed them a few times bringing this to their attention but they haven’t replied or asked for it back. What else can I do , they don’t seem bothered. ?