Bill Escalating each Month

September 2015 I app**** for a Virtual Landline that comes with a modem in December 2015 i finally got it to be active after numerous trips to my store and countless hours of queueing. My premiums are set at R405 per month for 24months and the service is also capped to my surprise my premiums have gone up to R1375. I called the billing section and they promised to investigate and come back to me but up to now there is no feed back and it's been 2months each time I call I hold for long periods with no real solution. Can anybody from Telkom please help.