ACCOUNT PROBLEMS

Since my upgrade in January 2021 my account is a mess. After how many calls and emails nothing happened. One contract with 2 phones. One was upgraded in January the other one in March?? Why not at one time. Then I was billed for Jan to Feb on the old contract fee and I was billed for Jan to Feb on the new contract fee..... in other words double charged. Then with the upgrade in March it was exactly the same. I was billed for 2 contract fees on ONE phone in ONE month. By email or phone you dont get further than the call centre. Every call or email a different person gives you the answer they see on the system. It seems like no one is able to the problem. Is there someone in the accounts department that can give me a contact number