Worst service I have ever received

I am shocked and dismayed at the level of service I have received while trying to close down my BT account which I held for over 15 years. I have always been a loyal customer, paid on time and never had any reason to contact BT until my marriage broke down and I was in a situation where I had to close down my account. Due to a recent upgrade I was still in tie in period which I was advised of on my initial call. This was approximately £250, which begrudgingly I had to agree to pay. I asked BT to close my account down and advise me of the total amount outstanding. After some discussion and time while the representative looked at my account I was told the final amount to pay would be £54 I questioned this at the time as it was so much lower but as it was confirmed again and I knew I had overpaid on occasions I believed this had all been taken into account. I was told there is a 31 day notice period and then the account would be closed and the £54 would need to be paid and that would be everything. 2 months later, endless calls, and more inaccurate information and mistakes made at BT's end my account has still not be closed, they have added on more charges and I now have to pay an additional £215 cancellation tie in fee. When I disputed this I was told the notes don't reflect what I am saying. And that the calls I have said I have made are on not on the system, nothing short of calling me a liar. I have since spoken to a manager and the complaints team and they all seem to think that the service I have received has been acceptable? I'm completely lost for words and my advice to anyone thinking of of joining BT is to avoid at all costs and anyone already with BT, make sure you take the date time and details of the call or communicate in writing so you have a record of what was said or agreed. This will avoid you being told you never made contact with them, when you did or the incapable person at the other end didn't bother to actually enter into your account details, therefore no record of your conversation is held.