INCORRECT BILLING

My usual bill for data amounts to R157.49 (capped) it cannot go over. 25 May I get a bill for R417.49. Phone in report it, I was advised my account will be credited. 24 June I get another bill for R417.49. Phone in and query my first complaint which had not been attended to which then got escalated. they then advised that my second query regarding my bill for June will be worked on differently to the May bill as they cannot work on 2 bills at once. on 02 July I was credited with R327.10 but was still once again deducted for R417.49 which is the incorrect amount. My second query is still being attended to. BUT LOW AND BEHOLD what do I get today but yet another invoice for ONCE AGAIN R417.49. First of all if you do the simple calculation of the two months that I paid R417.49 x2=834.98 when in actual fact I was only supposed to pay R157.49 x2=R314.98. I was credited R327.10 which means Autopage still owes me R192.90 but they have the audacity to bill me ONCE AGAIN FOR THE INCORRECT AMOUNT.