See if theres any faults here ➜ https://community.giffgaff.com/t5/Using-giffgaff/Force-the-change-of-SMS-settings/ta-p/4871794
● Also: Hand clean the sim (Very Soft)
• Other Possibility •
You could also be in a bad area for receiving a good Signal/Service if it is fine at other locations (if all of my info hasn't solved it)
• If A Mast Is Down In Your Area •
● This is no fault of giffgaffs,this would also effect members on the O2 network and anything that's run with O2 in your area so it's down to the O2 repair team to fix it and to update there website,the O2 website gets updated every hour so it's best to keep checking it or you could search the O2 forums within your area search and see if there's a clearer explanation.
Or you could think other options if your still unsatisfied with giffgaff reception etc.