Pre pay phantom Debt charges

I have A prepay electric meter. Three weeks ago it was displaying £12 (for “debt”) prior to topping up (the week prior to this it charged £6) which I was shocked at as I’d put credit on the week before. Last week - it demanded £16 for "Debt prior to being topped up with yet another £30.
The standing charge went up by 40% to £2 per week - this does not account for the 700% increase being charged via “debt” taken from top up’s. What is going on.

I have NO Debt - neither have I ever had Debt on any meter.