Orange / ee bill dispute

Hi, I'm hoping you can help....I'm having major issues with Orange / ee. I've been a customer for over 10 years and up until July had no issues with their customer service. I went to America in July and about 2 was after returning was contacted by orange to warn me about my bill which was £850. I was shocked as I had bought a bundle prior to travelling and thought this would cover the majority of my costs abroad. I was also careful to keep the phone off for the majority of time. A attempted on numerous times to contact orange to investigate the costs but couldn't get round or was promised a call back from a manager which didn't happen. I pay the undisputed Amount of £50 which left the disputed amount of £800. i tried to escalate a complaint but had to speak to mgr to do this and as they never returned my call I couldn't take it any further. Eventually I could a call saying the fault was at the orange end and it looked like my bundle hadn't applied so I would receive a credit of £800.... I thought that was the end of it...but no....see part 2 of my post!

Part 2....this week I received an automated message from orange saying that unless I paid my bill my credit rating would be effected and a bar was put on my phone. I phoned their collections teams who said my bill was over £2000!!!

I was in a state of shock and then had to chase orange for 2 days until I got to the bottom of the issue. Orange had done debit instead of a credit to my orange account so I now had the original £800, another £800 and a mystery £490 which was apparently further charges from America! I'm trying to get the £800s sorted out and am now back to square one disputing the £490!! I am waiting for a mgr to call me back as the call centre staff can do nothing....no call so far.

My issues...
1. I was originally told I had used 100mb of data at £8 per mb in US hence the cost of £800. They have removed this cost saying they had an internal memo saying these charges no longer apply to customers for use of foreign networks?
2. Now orange are saying I have used 69mb...totally different to the original info and I owe £490
3.reading through previous posts if I ask for a subject access request can I receive transcripts of my calls and prove I was given miss information?
4. I want to leave Orange and break my contract as I'm totally fed up....can I do this under the consumer credit act? My phone has been barred for nearly a week so can I prove that as these charges are not valid that orange have failed to provide the service I have paid for?
5. Basically totally fed up of mis information, bad customer service and poor information....
Can you help me as this is totally stressful and I just want to resolve the situation and leave Orange....
Thanks