Cheat clients on contracts

Just a friendly warning to my fellow Vodacom users, I experienced the last 4 months that Vodacom is cheating me on my contract. I am currently on 2 ,Top up 350 contracts whereby I am supposed to get R350 value on top-up value that is left the previous month and the last few months I only receive the value of R 229.07 on the one contract and on the other R165.71, so in total they are cheating me with the amount of R305.22 per month