Are you on 4g or 3g?
Try resetting network settings chels49764
Check coverage here for any mast issue http://giffgaff.com/coverage-and-service
If persistent, pop message Agent here 🔻🔻🔻
Reply will here ⏬⏬⏬
giffgaff as MVNO, use O2 bandwidth, which has increased recently, so data speeds should be faster than previous. However, as with all networks, during busy periods, the network can suffer from congestion and as a result, data speeds can be reduced.
To try and improve your current data speeds, please turn your phone onto airplane mode then back off again for it to reconnect to the network, or simply reboot your phone