VODACOM'S SYSTEM IS *** AND THEY DONT KNOW WHAT THEY ARE DOING

I am a customer of vodacom for 13 years maybe more and have a on going account with them.For the first time they let me know that my account is arrears that cant be possible,when i phoned them regarding the problem the lady told me i am a prepaid customer and not a debit order client!!how can they just move or change thing like they want.They debit every month the last day of the month and then on the 3rd of the next month there is 3 more debit orders that needs to be deducted, they tell me it is because of insufficient funds how it's possible i don't know because how can that go of on the 3rd 3 days after vodacom needs to deduct there is no money in my account they full of **** and there system is **** they just do what they want and carry on and then we need to struggle.