Help Switched to the Galaxy S3 and can't make calls/texts

Hey everyone,

Just switched to the S3 from an iPhone 4S, absolutely awesome phone!
Love being back on Android.

Big problem though, when I first started up the phone I connected to Vodafone straight away but couldn't call or text. Then it just dropped to Emergency Calls Only. No connection to Vodafone.
I went out after that and the phone picked up Voda again and showed that it was connected with HSDPA . Still wasn't able to make calls, send texts or connect to the internet. Rang Voda and the guy didn't exactly fully understand me. He's ordered a replacement sim card for me but I'm fairly sure this isn't a sim problem since it does pick up Vodafone every now and then.

Tried setting the phone to GSM networks only, tried finding searching manually but just says Searching for a while.

Just really want to get this sorted as apart from this I'm loving the phone. Any help would be massively appreciated.