Being overcharged everymonth

I don't knw wat I dd to vodacom I hv bn a loyal customer for many years but lately they over charge me things I dnt even knw about... Everymonth I pay extra cash that doesn't even make sense I payed my bill last month nw they say my account is in erease I dnt even knw hw or y because I payed with thier app n the money went thru... This is unacceptable n is happening everymonth