Issue with porting number no working phone

Informed my port has been successful last week, but still the phone is saying Invalid SIM card, Network locked SIM card inserted.   Please help I am at my wits end and it is coming to the end of the month with accounts to pay.  Seriously thinking of going back to my old provider at least they provide a service and contact numbers.  I am not at all technically gifted and find this utterly unacceptable.  Perhaps you need to rethink your advertising as it is confusing even to contact "support".  A response would be appreciated.