Disgusting Service / knowledge

I have a limit of R100 set on my account. On the 19th May i was soft locked as i was over by R149.13. i called the call centre for assistance but was passed from pillar to post and then was hung up on several times. I then send in a complaint and was contacted by Clinton Neill. he then raised my limit to R200 i immediately received a mail saying i am over by R228.41. I was a Nashua customer fro more than 6 years and never did i experiance this. i never exceeded my monthly limit either. Clinton could not tell me if i was over by calls or data and when he checked his system it showed i was owing only R109 he could not explain this either. in order for me to be unlocked he eventually had to increase the limit to R400. he said it is a billing issue. I even went instore to the clear water branch and was assited by Winnie who also was unable to assit me. i am now sitting with a bill of R605.94 for the month of May. why am i liable as i could not get assistance? i also sent a complaint to Clinton but was told to contact the credit department. hello my bill is so high and you still want me to call around? i am now struggling to port my number to a different service provider as well