Telkom is charging for already paid bills.

Telkom has billed me in April after waiting two months for them to install a voice line for internet. I paid that bill. now i was billed for may with April's amount included. how can such a big corporation be so ***********? All this nonsense and my internet connection isn't even stable, every hour my connection is lost for a few minutes. I am so tired of this corporation, i tried their call center once and waited 45 minutes before i got the call answered and another 15 for the person to help because i was put on hold again..If i had other choices for internet i would not go with this business.