Does it come and go (so you have signal sometimes but othertimes not) @Denzil2 ?
It might be the sim card has some static or dirt on it that affects the connection to the phone.
Try taking it out and cleaning it with a soft cloth.
If that doesn't work you could try your sim in another phone - if no issues then it might be your phone.
You can swap your sim at your local o2 store (take photo ID), or ask customer services to send a replacement - they do turn off your current sim card if you do it this way, so you might be with NO signal at all while it is in the post.
Also see if these help:
Guide: How can I sort out my network issues?
Guide: Is the network down for me or everyone?
Please note, this is not customer services and we cannot access your account. Do not publish personal details (email, phone number, bank account).
Link to our guide on how to contact them can be found here
