So I was wondering if it were possible to switch my phone number back to my old Telecom SIM? I had a Nano SIM in my iPhone 5, but moved to an Xperia Z with a Micro-SIM.

I want to go back to iPhone for a bit as I get bored easily, but rather than buy a new SIM swap, can I just get my number moved back to the old SIM? Its still sitting in the phone from when I last used it, entirely useless at the moment.

Thanks, 
Sam