Discovery not interested in agreements

Due to an administration mistake in 2017 I was having a dispute with Discovery about R350. Finely in August September the matter was, what I thought, resolved. This year 2019 in January I get a call from Discovery. We are back to the R350 again. They were full of apologies and asked if it will be okay if they deduct it in 3 installements. Out of pure desperation to get this matter resolved once and for all I agreed. Then I told them to take all in one payment on the 15th February as that is when I get my pension. So said so agreed. Now they suspended my medical aid until they have received the payment despite the arrangement. Why was I not informed that I will be suspended until it is payed? What if I agreed to the proposed 3 installements, would I then have been suspended for 3 months? I was suspended in 2017 because of the admin fault which was lifted after they discovered the fault. Now again. Shame on Discovery who can not honor an agreement and can not correct admin faults. Very upset.