vodacom ripping people off once again

I took out a contract on the 22 of feb and on the 29 th March i was debited for the the full asmount plus a loy more that the branch couldnt figure out , in other words i paid to much . But then that is typical of vodacom , then today i get debited for april , this is disgusting when they cannot do simple maths and pro rata fees and the 111 is as helpful as a *** in dwang . why do they think they can just do as they wish, i find their srevice disgusting