Repetitive Abnormal debits.

Repetitive abnormal debits since January 2020. The debits are raised as i have notice a less than normal debit that went through on the 15 January. I called in and the matter was resolve and was guaranteed that as from the 15th February my usual premium will continue as normal. To my shock more than twice the figure of debit went off on the 15th February. I engaged and a less refund was done to me, thus the refund is short. Today, the 3rd March, a debit of my normal premium is gone off and i find my back account on negative balance. I did not expect such debit since my debits are on the 15th of every month. I have been engaging and it is tiring.