New contract instead of upgrade

[smish]

Hey,

I bought a new contract today through Mobiles.co.uk which is still on o2 but has a new number (rather than an upgrade). I'm going to ask customer services to transfer my old number to the new account. 
I can see what my new number is on the order form, but I haven't got the new phone/SIM yet. Can I start the transfer process now so it is ready, or do I need to be in possession of the new phone and SIM?

Also, do I put the new SIM in the new phone, or keep my old SIM?

Thanks in advance!

[MI5 · Accepted solution]

You just need to call O2 on 202 and it will be migrated within an hour or so. Best to be in possession of the new phone and sim when you do it.

[smish]

Thanks for your help. Would I use the new sim or put my old one in the new phone?

[MI5]

I'd keep new sim in the new phone and transfer your old number to the new sim. That way, you get the new tariff too without any need for further changes.

[smish]

Awesome, thanks for your help!

[MI5]

No worries mate.