It's likely it's a faulty activation
Do this check
Take your sim out of the phone and take note of the sim serial number on the back of the sim
Log in hereHttp://j.mp/activate_sim
Put the first 19 digits from the back of the sim in the box provided
( NOT the 6 digit activation code)
And click continue
It'll either say the sim is already active ,
You cannot have two active SIMs. Activating a new SIM will deactivate your current SIM.
If it says the latter, you know the activation is faulty, what you should do now is carry on with the sim swap/replacement proccess
Click where it says...
"Yes I want to replace my SIM"
( on mobile browsers don't forget to scroll down to see)
On the next page click "yes I'm sure"
Your sim will hopefully be active within 30 minutes