Incorrect billing

Have been trying to sort out a billing matter with vodacom for the past month, have been to the gugulethu mall and all also been on phone with them for the longest time. I just dont get how you can charge someone for a handset they finished paying for and claim that you are charging then in arrears Mind you the apparent arrears are 2 months behind!! I have had nothing but the worst customer service from this company, agents kept me on hold for so long just because they couldn't explain the charges i was querying. Not to talk about being blind transferred to other people whom i have to explain ma situation again cause the previous adviser cannot explain the charges. I have been with this service provider for more than 5 years and j wonder how many incorrect charges have i over looked because i trusted them not to be ******. Very pathetic customer service indeed vodacom!!!!!