HOW VERY STRANGE THIS IS.
I am experiencing EXACTLY the same issue with talktalk! (AOL)
I had exactly the same kind of fault in October 2011, continual Broadband disconnection and slow line speed which they said would be rectified at their end but then wasn't. They said I needed an engineeer from BT. He never turned up and the problem mysteriously went away without any BT engineer visit. Now (Feb 13th Bill) I will be charged £129.99 for a non existent BT engineer visit. They claim one came and I wasnt in so I must pay. I am still awaiting a call back. The call centres have no clue what is going on and there seems little come back possible. It seems VERY ODD that the exact same fault happened to me and the exact same charges for this are now being levied 3 months later.
I have rang them, e mailed them and written to them. Unfortunately I have a contract until Novemeber 2012 otherwise they would be history. I feel like they are tryio rip me off and others it seems. The call centre service is also appalling.