PAC code, new sim. Help!

[LHRFlightman]

I am taking my mobile number with me when I leave my job on 31st July. The number is 07909xxxxxx and I have a PAC code. When I signed up with O2 on Thursday I submitted my PAC code and my number. They have sent me a sim with a new number which is now in my phone along with my old sim. I have a dual sim phone. What happens next? Does the old sim get turned off and the new sim become 07909xxxxxx?
I've had this number for 17 years so never had to do this before!

Thanks.

[Mr E]

Your old sim will stop working in the next 24 - 48 hours or so

Your new sim will become your transferred number.

You throw the old sim away.

[LHRFlightman]

Wow, as easy as that? Thanks!

[blingybongy]

LHRFlightman said:

Wow, as easy as that? Thanks!

In theory.

[Mr E]

blingybongy said:

In theory.

In theory.