Contrabutions Changing

i took a bonitas medical aid out on the 1st of march my contributions were R643 up until the 1st of June,i decided to look at membership certificate today noticing that my contribution has been increased to R3106 with no communication being sent to me at all, i gave bonitas a call and i was asked if i sent my documents through, they could not give me a valid reason as to why it has increased and i asked what if my debit order now gets rejected as i did not budget for R3100 i was told my medical aid will then be suspended, i have been paying R643 for 4 months and now there's been a capturing error, i was just told to call after 5 working days to query my contributions which is unacceptable.