Thank you for contacting the giffgaff Community.
If you have just registered or setup a new or replacement SIM then this can take several hours to complete, it's rarely instant and usually Data Service comes before Calls and Text Services fully activate on your SIM. SIM activation usually takes 30 minutes to 4 hours, but in exceptional cases might take up to 24 hours.
Your number will be shown on your Account Dashboard https://giffgaff.com/dashboard and sent in a welcome message as soon as the SIM is ready to use.
Also, try restarting your handset periodically, this often helps to get service working too!
If still not working after 24 hours Click, here for assistance and ask an Agent to look into things for you https://support2.giffgaff.com/app/ask/Calls-texts-and-data/My-services-arent-working/form/ often reply within 4 hours most cases but can take up to 24 hours in busy periods. They do work 7 days a week from 8am to 11pm.
Find agents reply here "Messages: From Agents" which is half way down the right hand side of your "My giffgaff" page. Or via this link https://giffgaff.com/support/questions