"Not enough help with oxygen concentrator electricity bill"

I have severe chronic obstructive lung disease and as a result use an oxygen concentrator at home which uses electricty. I do not have to pay for my medicine and part of my service from my oxygen supplier is a rebate for electricity used.

But my supplier is not refunding the full cost of the electricity used and is in breach of the law which says I do not pay for medicine costs. They have, until August, been paying only 10p per unit when my costs were 15p per unit. Now they are paying 13p per unit when my costs, on the lowest tariff that I can find, are 18p per unit.

I am, surely, not the only person this is happening to and we must use the equipment supplied or die in our sleep. Surely there must be a way to meet our costs so that we do not have the added concern of cost on top of our need for oxygen. Anxiety only increases our oxygen usage!

Has anyone else got in touch with their PCT and supplier to try to solve this? I have to do it each time there is a rebate! I should not have to battle to have these legitimate costs met.