Performing a SIM swap - what happens to the old number?

[biscuits99]

Not strictly an O2 query, as its for Tesco Mobile in my case, but I was just wondering about this process.

I had a very old (around 2012 or so) full size PAYG Tesco SIM which was working fine, I then bought a new phone and ordered a new nano SIM from Tesco on PAYG.

On the new nano SIM I paid £10 and activated it, then ran through the SIM swap process:

This worked and the original number ported to my new Nano SIM.

My question is what happened to that number and the credit that was on the nano SIM?

And as I just needed to provide the SSN of the nano SIM, if I found someone else's SSN, could I just 'overwrite' their number - I don't remember the nano SIM number asking me if it was ok to proceed, that check only went to the original number I kept.

I mean, not an issue here as the process worked, but a bit odd it just seems to overwrite a number without checking?

[pgn]

Community guides for moving numbers below for ref.

Guide: Sim Swap: a mini guide 2017 update and Guide: Migration & porting into O2  - the number has to match the SIM SSN - the old number that was on the SIM you have swapped to goes back into the available pool of numbers for eventual reuse @biscuits99 

[biscuits99]

Thanks for the info about the number going back to a pool. Do you know what happens if someone finds your SSN though - could they push another number on top of it without your consent?

I didnt get any sort of check against the destination number.

[pgn]

The SSN is linked to your account, which in turn is associated with your number, @biscuits99 -

Answer to Can you keep your old cell phone number if you replace your SIM card? by Paul Crowley https://www.quora.com/Can-you-keep-your-old-cell-phone-number-if-you-replace-your-SIM-card/answer/Pa...