How exactly are you trying to share the contact?
Email, iMessage or SMS?
http://osxdaily.com/2012/02/01/send-contacts-from-iphone/
Maybe it's trying to send it my iMessage but iMessage has not been enabled/activated?
iMessage activation can require a UK SMS costing 25c from your cash credit balance to be sent first.
This is a common problem down to the way that Apple manage things - nothing to do with 48 per se.
Hope this helps.
