Horrible Service!!

Worst service ever!!!!!! I have been a loyal customer to Vodacom for over a decade!!! My contract expired end of May and I didn't upgrade and went over to pay as you go. 2-week back I decided to upgrade my phone. I went to Vodacom in Centurion Mall, the sales lady just said sorry we cannot upgrade you due to an outstanding amount on my account. This wasn't possible as my account was deducted via debit order, after basically asking her nicely several times to please check as this cannot be possible, she eventually phoned customer care with a very rude attitude!! Customer care informed us that the mistake is on their side and they will rectify the problem within 24-hours. Last week I tried upgrading again online and once again was informed by credit score was low due to an outstanding balance on my account. I phoned today and spend 90-min on the phone once again with NO luck, every consultant I spoke with just transferred me to another department!!! How can your service be so bad??? This is a mistake on YOUR side but not one of your staff members are willing to help and assist me to fix your problem! I am really utterly disgusted!!!!