Refusing to downgrade

On the 30th of November I upgraded my subscription to Premium. I have informed the agent that was assisting me that the upgrade was ONLY for December. He told me he will schedule a downgrade immediately. To my surprise on the 1st of January I am told I must pay R850 it’s due. I do not have that amount the upgrade was only done for December for visitors and they provided for the money. There’s no way I can pay that money can you put me back of my subscription of R29 that was on