4G SIM in 3G phone?

[aca95pks]

I just upgraded my plan since I can now get more for the same cost. I've been sent a new SIM which I assume is for a 4G phone. I haven't yet got a new phone, just my Nexus 4. Will the new SIM work in this phone or should I just continue with my existing SIM until I actually get a 4G phone? Cheers, Paul.

[Anonymous]

Oh my god 2g that's what I'm using now aswell it's like a rare time that I can get that speed but I hope that o2 sorts this out otherwise I will have no other choice but 2 go for other options which I do not want 2 do...