Replacing old PAYG phone, how retain number?

[AChappie]

I am in the throes of replacing my ageing iPhone 4 with an iPhone SE.  I use very little or no data and have a Big Bundle on the old phone.  I am not buying the phone from O2 but wish to put a new Big Bundle on it - how do I keep my old mobile number or do I have to have a new one?

Also I assume I will lose everything that is on my old phone and will effectively have to start from scratch with the new one?

Many thanks in advance - this is the first time I have changed phones in many years so am not at all up to speed on what to do so any (polite!) advice is welcome.

[MI5]

@AChappie 

You'll need to call customer service for a new nano sim with your number and tariff on it.

Backup your iphone 4 to icloud and then when you get your new sim, insert it in the SE and restore your phone from your icloud account.

[AChappie]

@MI5 

Many thanks for the swift response.

Ref restoring from backup to the new SE - my iPhone 4 is so old that it stopped updating iOS at v6.1.3!  I have since been doing local updates onto an elderly laptop via an elderly version of iTunes (which I had to stop updating after warnings that future software updates would make it incompatible with my phone).

If I can restore via the elderly iTunes onto the SE that's great otherwise presumably I will need to get a new number for the SE in which case how do I do that?

[MI5 · Accepted solution]

@AChappie 

No need for a new number at all.

Your sim can be updated to a nano with your current number and tariff on it.

I was aware of the issues with the iPhone 4 and iTunes which is why I believe you can back up to iCloud and then restore from that backup to your SE to keep all your info off the actual phone.

Unfortunately, I can't remember if the 4 can use iCloud so you'l have to check in your settings.

[AChappie]

@MI5 

I have checked and it is not set up for iCloud at all - I suspect that's why I've been doing the iTunes backup all these years.  So do you think the SE will accept the iTunes backup?  And, again, if not, how do I go about getting a new number if I have to go down that route?

[MI5]

@AChappie 

You don't need a new number. You just need a new sim which you can get by calling customer service Guide: Coronavirus Community Help and Support 

Honestly, if the 4 won't back up to iCloud, I've no idea how to get your info transferred over easily.

I guess it will be a case of copying contacts over one by one.

Pictures and videos can be saved to Google photos and transferred across that way.

[AChappie]

Ah OK.  Yes I think I will have to copy over the contacts one by one, no bad thing probably as they could probably do with weeding out.

Many thanks for your help and advice.

[MI5]

Best of luck mate.

[AChappie]

Final update - got a new sim then requested a sim swap.  Omitted to backup the old phone before doing that so have lost about a month's worth of info but not a big deal and at least I don't have to sit for hours putting in all the contacts.

Doing the restore to the new phone was a bit of a palaver - new phone wouldn't speak to old iTunes so couldn't get the option to restore.  But found where the backup file was, copied it onto my newer pc and current iTunes, connected new phone and they spoke to each other so got the restore option which went through ok.  BUT the restore was to the old phone's IOS 6 (!) so then had to upgrade to IOS 13.

Phew!  Anyway, all done now just fiddling about with settings and preferences.

Many thanks for your help and patience.

[MI5]

@AChappie 

Good tip there for the backup and glad you're sorted