Contract confusion

Hi, can someone explain this for me please?

My original contract was ~£139pm and then expired earlier this year. I was offered a new contract of ~£108pm which I accepted on April 15th. Come April 28th (the 28th being around when the bill is settled) I was charged the usual ~£148. I thought this might be because I accepted the new offer part way through the month and being sort of in between a rolling contract and a new contract and would have to wait until the following month for the new price to be, well, the new price.

However, I logged into my account today and seen my bill is due on May 28th, but my new price is ~£145pm...but only sort of.
This is what my bill for the 7th-28th of May says on my account at least, despite of course accepting a new offer way before that. 
On the timeline of my account it shows I changed my package (which I assume is accepting the new contract because the package didn't change) on April 15th. I was given 50 pence credit, for reasons I don't understand, at the same time. Then later in the timeline it shows ~£145pm for my current package obviously.
Then there's more confusion because when I check the contract on my virgin account it says the contract start date is April 15th 2025 and the amount due every month is £0.00 (this of course being the preferred amount :P).
Then to add further confusion the contract which was emailed to me states my new bill is ~£108 from April...2026.

I mean am I the idiot here because I just don't understand any of it at all.

Thanks.