switching Sims from same network's

[XPERIAUK99]

I am using a secondary SIM from my network (tmobile UK) and I have my main SIM with unlimited data. I used my seonday one to set up phone l. Will switching Sims work as this phone is an upgrade, will my plan change to my main plan and will I have the same number . Thanks

[XPERIAUK99]

It's cos my SIM acting weird

[Danial-mach1]

You must ask this from your network carrier