struggling to get a account payment letter

i had an account with netcare kuislriver the account was paid last year i spoke to the lady called Mathapelo and she gave me the account number that i neede to send the money to. few months i still receive calls demanding the money and i have been making endless calls regarding this issue and i was told that the money was sent to the hospital account. im struggling to get through account department im using my damn airtime making useless calls why are you guy making my life so misreable while your money was paid last year already. i need someone to call me with regards to this payment letter that is taking long for you to send. your service is pathethic