Unacceptable service

I received 32 calls from 3 different numbers for a R 60 short payment. They call you and when you answer the call cuts . I answered 2 of the 32 and the consultant was not helpful . Yesterday and today I tried their 021 no. N0 reply. Oh yes on the new statement I see a R21 interest fee added already for the R60. I need assistance from your account dept . Head of credit pls.