MRS NL Maloma

I am having problems with my data contract from Telkom i am being charged more every month and i don't even used the whole 80 gig the give i cancelled the usage of airtime now i need to know how does the bill goes from R209 per month to R260 last and this month invoice R294 ....now i tried calling the billing DEPT am transferred from pillar to post .....am being put on hold for 30 minutes