New mobile questions for the tech savvy

I'm getting a new mobile phone delivered tomorrow which I ordered online from o2. I've never done this before, normally I go into the shop and they sort everything out for me. I finished paying off the current contract ages and was due an upgrade which logging into my account recognized when I purchased it. I have also stated that I want a new sim as I spilt coolant on the phone a couple of weeks ago and a few days later it broke so to be sure I want to fit the new sim as well. I assume when I get the phone and put the new sim in the number will be different... Or does the fact that I'm refreshing the contract mean o2 just swap the number over? How hard is it to swap the number over myself? If I stick with the new number would I end up paying for two phones airtime plans? I would ring o2 but the phone doesn't work and I don't have a landline. Any replies much appreciated.

You need to get a PAC code from your existing line supplier then provide this to your new provider. This will tell them you want to keeo your existing number

When i have changed phone/sim and not changed supplier my number has just been swapped over, i didnt have to do anything.

If you are staying with O2 and doing just a contract refresh then it should be fairly straightforward and you shouldnt need to do anything.

I messed this operation up somehow with vodaphone a while back, i ended up with 2 sims and numbers for an upgrade that there shit website screwed up, so they were charging me 20 quid a month extra for something i didnt want so make sure you dont get a new number.

Sorted now just a refresh. The new sim came with instructions, it did say to wait until the old phone stopped working (stopped getting service from o2) and put new sim in new phone. The old phone didn't work so I just turned it off for 2 hours then did the sim swap and it all went well. Had to do at least 4, maybe 5 updates to the new phone which I thought was weird.

Naa that sounds about right for the phone updates, you have to remember that phone could have been sitting on a shelf for 4 months before being switched on - lots of updates in those months come out so...
Same with pc's folk think it odd the first thing a pc or console does when the take it out the box is immediately go looking for updates but its completely normal and does need to be done.

I just thought it would go straight to installing the latest update but now you've said it, it makes sense to go through them all because some updates will do certain things that the latest one doesn't need to do.

Some updates can be skipped but others need to be done as prerequisites , there are also updates to the applications built into the phone so it wont just be the main OS being done.
Similar to the windows update world, you cannot install certain feature packs for windows 10 unless some updates have been applied first although the all in one 20h2 update assistant i have been using for machines here recently does actually bring them all in together and do it as a one job hit which is a bit nicer than pratting around with dozens of updates.