urgent

i have a problem with vodacom, i have been double billed for two months now and whenever i call to inquire am told they gonna log a call for my problem then after many days i will get a lousy sms giving me senseless explanation. bill for month july and august are been double charged. i took an airtime advance which i paid it up on the 26th july 2019 and it still appear on my bill and that is exactly what happened the previous month. can anyone save me from this kind of theft naa, can anyone come with a clear explanation on why am i been treated like that