I've been using a 3G Sim in a 2G phone & its been working fine.

Today I've received an alert from my phone company, 3, telling me that in 5 days my Sim will not work in my 2G phone & that I need to ring the number provided to purchase a 3G phone.

Is this a scam or can they do this?

I never knew there was a difference. It's all done at the phone/operator level and not at the SIM level.

Anyone else know?

Thanks for that response.
Has no one else had this problem?

A 2G SIM won't work in a 3G phone. Never heard about problems the other way round. I'd ring 3 customer service and ask them to clarify, BUT NOT on the number sent on the text!

I would imagine they can not do this however its probably a better idea to get a 3g phone anyhow because with a 3g sim in a 2g phone you cant take advantage of the 3 services ie video calling.

I did have a 3G phone, but gave it my partner as he had broken the screen on his & I went back to my old 2G phone.
Phoned 3 today & was told they like customers to be able to take full advantage of all the facilities of a 3G phone so they would be making all Sims incompatible with a 2G phone.