Discovery contributions

I got a E-mail on Friday saying to verify my income which I already did last year so I tried to do do that as a pensioner I'm happy to pay their new contributions of 1961 so there was boxes so as I put a right mark on the box my income is not more than 0- 10 000 . I then got a E-mail stated that my next contributions would be 3662 ,I phone several times my airtime got put through one person to another person then my airtime got low ask the lady at Discovery please can they call me back as my airtime is finish a 100 rand just on Discovery with no issues resolved, Discovery shame on you for wanted to take from a SASSA pensioner 3662 rand as my contributions was first 1810 then went up to 1962 which I'm happy to pay but 3662 I won't be able to pay as I'm not phone savvi I tick the wrong box please need help because I'm paying my medical aid instalment with my SASSA money and can't afford 3662.