The Great Utility saga!

jimmylove_2

I used to be with NPower for gas and electricty and never had any problems.I decided to change to Powergen for they provided the cheapest rates at the time.During the cross over period gas work was being done in the street and relaying a gas main and a knock on the door by the engineer told me I needed a new meter which he duly fitted. Then the problems started!!!!
For approx 3 months I didnt receive a bill for gas or elec so I called Powergen up and asked for the bill..nothing arried.Another month went past and they promised to get a bill,again nothing arrived. To cut the story short, it went on for about 8 -9 months with threats to go to OFGAS etc when they finaly sent a bill out.It appeared that they had let a child play with the computer for the day,hit lots of buttons on the keyboard and then add a few 0's to the total bill. I cant remember what it was but something in the region of £3500! (i live in a 3 bed semi,both my wife and I work all day and the kids are at school) so you would expect the average family gas and electric bill .Following lots of calls,letters and conversations with OFGAS they sent out meter readers who took meter readings and stil came up with theis ridiculous bill which I refused to pay.Finaly someone with some sense came out and he said that I was paying for number 33,33a,and my house number 3's gas and electricty bill.How this happened I do not know but his guess was the chap who fitted the meter,hadnt input the details correctly of my meter number and got my adress dwrong also and somehow I was paying for all the street address that began with the number 3?!?! Powergen to be fair were very good in the end and cancelled the bill and then esitmated what I would have used for the 9-10 months which total about £700.They said i could have it intrest free and pay it off as and when.I currently pay about £20 more on my bill to pay this off.
Are you still with me??? Then ill continue because here comes my question to you kind folk who are still awake and havent lost themsleves in this confusion or pressed the back button at the top of the computer in boredom.
Powergen are now one of the most expensive suppliers and I wish to change to a different supplier but I cant afford to pay of the outstanding £600ish I still owe them. Would I still be able to swap do you think and leave the £600 is still owe to Powergen and continue with a new supplier or do I have to wait until I have paid this off in July 2020?
Here endeth the first lesson.