Over charged account

I took contract last year of a router wifi of R99 n last mnth l was charged R495 n when l enquire about it they told me there's something called 500mb data recurring added to my account which is R500 n without consulting me well l asked them to remove it then da consulted said she did then l received dis mnth statement saying by da end of da mnth they will deduct R800 instead of R99 n l only used da router on da 7th of July cos l already had data dat l bought m so confused honestly cos l took a R99 contract nt knowing l will b paying for other 8people without knowing n wht **** me off when l try to settle da account l was told of R800 extra money like seriously wht da **** is wrng with Telkom pls reply????????