Banging head on wall because of Scottish Power

Viberduo

I have a older dispute with them and a new dispute with them for identical reasons but new address.

In address 1 I was with them 3 months and topped up about a fiver a week as not in house much as went to local place which had free wifi, sofas, tvs etc and meals that they didnt make profit from to keep warm I then changed suppliers to one with higher unit charge but lower standing charge so saved a litte(a quid or so a week)

After I moved suppliers I was billed standing charges for the entire period for a PRE PAY meter despite the meter taking the entire standing charge off daily(I know this as went away for a week a few times and everything was turned off and trip switches off etc and it took off to the exact pence the weekly standing charge)

It says a lot when my next supplier never sent me bills for standing charges.

Anyway I moved house and new place had Scottish Power which I knew would cause problems so 2 weeks after moving in changed suppliers which took a month and topped up as usual.

Just got a bill through for you can probably guess, standing charges from day I moved in to day I changed supplier!!!!

How can they fail on so many levels.

The ongoing one I got a reude debt collector ringing up and the usual "we are right you are wrong" attitude and refused to give me evidence of the debt, and after a lot of arguing sent me a copy of the "bill" i.e all it said was standing charges, the 2nd one said estimated usage despite me giving meter reading when I moved out to old and new supplier(which showed like £15 in CREDIT!) I lost this credit when I changed supplier for some reason(it reset to £0)

What can I do to get through to these people.

Viberduo

Got a letter today saying I owe them money and must pay it or it will be passed on to debt collectors(the newer one)