Hello you can only get speed that’s available where you are in relation to. Mast ,
not everywhere gets good signal ,
couplr checks to do
irst put postcode here check for mast problems https://giffgaff.com/coverage-and-service#coverage
if if all ok try a manual roam to force network http://community.giffgaff.com/t5/Using-giffgaff/Force-the-change-of-SMS-settings/ta-p/4871794
also check APN if wrong insert
@glaswegianeric because a speed test image by itself tells the community nothing at all other than at a specific time, on an unspecified date, (presumably today), in an unspecified location, (although one can again presume this from your username), somewhere in the United Kingdom those were the speeds you were getting.
It is not much to go on even with the assumption that you conducted the test in some part of Glasgow, at lunchtime, (when everyone would be on their phones, supporting what @woodyuk said about congestion), especially in reference to the assumption hinted in the subject line about throttling.
We don't even know which package you're on, which is relevant because if it's the £25 one giffgaff are open about the fact that they do traffic manage that particular product.
You can't go totally on the signal bars on the top.
It's best to go into settings then about phone then SIM status
Even with a signal like mine which is really bad at the moment 1bar
-108 they say over 101-105 you start getting problems -75 is about the best you can hope for.
I still get download speeds decent sometimes a lot better.