Nightmare upgrade

One of your agent called me to upgrade my contract , and at the end we agreed to upgrade to contract what i was on instead of what he was trying to sell me .. than on my next month bill i saw that my contract was downgraded to what he was trying to sell me and i was out of data i went and than purchased extra data and meanwhile i called into do am inquiry about it as to why my contract was upgraded wrongly and they need to go and listen to voice recording ( rco477121) reference number for that dispute . And a week later they called me back and said my dispute was correct and they will change it back to my original plan which o wanted to carry on with . (400 gig price plan) that was the end of it and i assumed it was sorted . Only to find out 2 months later i was not put on any contract and i was now being charged out of bundle rate for the past two months !!!?? What kind of service is this why are you guys even calling me if you not going to upgrade the contract as i wanted it ??? Not once but twice ??? Who is going to pay the bill of the last two months that was out of bundle rates meanwhile I thought issue was sorted . Why was i not informed ?