Tell your staff to accept no for an answer

I do not want to be mean to people, but after i said 5 times that i am not interested in a upgrade because that involves me paying more on my contract i was interrupted multiple times and he did not take no for an answer, after the 5th time of being interrupted i told him I don't want to be rude and he started going off on me about no one is being rude, this is bad service and pushing clients that has been with you from the start is bad practise, get your staff in line.