Severn Trent bill confusion

cherryade44

Hello, last year my water bill was approx £800 and was paid in full in 8 installments. Very recently I received this years bill of approx £900 with 8 installments due of £113. So far so good, I enquired about having a meter fitted and was told there was one fitted recently in the street and I could be put onto meter readings within 5 days,so Using their calculations my approx usage would work out at £500 per year ,approx £40 per month over 12 months.
I created an online account which as of yesterday said we owed £900, then today I got email to say we are now on metered readings. When I logged on it says we are £413 in credit with future payments pending of £4 per month. So I rang up to ask why we were £400 in credit. The person said something along the lines of last years bill was cancelled so you were £800 in credit minus £400 paid, another bill is pending ,but couldn't telll me when.
I said I don't understand ,she said  what don't you understand and repeated it all. I asked if £400 had been taken from bank account, she said no, I asked about future payments she said £4 a month but this might be recalculated,. Does any of this make sense to anyone,if so I would like your take on it
Thanks in advance 

JGB1955

Looks like they have given you £413 credit for LAST year, so your ESTIMATED bill for 2023/24 will be (roughly) £500 minus the £413, payable at £4(ish) per month.  Yes, the numbers aren't exact, but looks like it's all in your favour and perfectly reasonable!

cherryade44

@JGB1955  thanks for replying. if they have actually refunded me all that money then I'm highly delighted. If I had switched last autumn I could understand that. Anyway fingers crossed you are correct. Thanks again