Shell energy disappearing readings and estimate

Jackie-s

I was swapped to Shell Energy a year ago when previous supplier went bust.  They are a nightmare.   Apart from grossly increasing the direct debit, I had no bills from when the smart meter for electricity was fitted - not gas but that is another story - in beginning of July til today 16th October.  I have been submitting gas readings religiously including one just before the increase but the gas usage on my much delayed bill is still estimated and at a much higher level than the actual reading.   I cannot access submitting meter readings on the website so go onto my phone app and find there are no meter readings showing from May 2022.  Where have the rest gone.  So I submit yet another which is lower than the May estimate.  So I have made yet another complaint but they get no=where.  What do I do next to escalate it