Bad service

Lost my phone and did a Sim swop on my *** which all of the sudden it's a connector been send from pillar to post for reversal since I can't make or receive calls on this number,I also did an upgrade which no agent is able to see on their side while their 084135/145 number can't get through....I need to check if the contract is cancelled and get a cancellation letter since I dnt want surprises month end ,can someone call me on *** I need this matter solved urgently....been a client for years I am honestly disappointed on the service I am recieving