Transfer of phone numbers

[EMF]

I want to transfer my phone number from an old PAYG Nokia to a new Doro 8050. I plan to continue with a PAYG tariff on the new phone. It seems that when buying my Doro from O2, I cannot buy it without a SIM, but I understand this SIM will already have a phone number allocated to it. Customer Services suggested getting separately a "Replacement SIM" and putting my old number on that. Seems

unnecessarily wasteful. How else can I transfer my old number on to my new phone? (The O2 Help on transfer of numbers deals only with how to do it whenchanging providers or tariffs)

[MI5 · Accepted solution]

@EMF 

If your old sim fits the new phone, just use it.

If not, you can easily do a sim swap Guide: Sim Swap: a mini guide 2017 update