Nobody can sort out a simple problem!

Went into a Vodacom shop, filled in the form to cancel a contract after almost 20years, had ID book etc.. asked to work out ALL fees to be paid so that there is no come back and paid 2 months in advance . Keep on getting bills for 3 months later and then they cut the service!!!! for non payment. what is the purpose of the forms, the person visit to the store.............?