I have an s22 ultra and have noticed for quite a few months my data is extremely slow almost to the point it isn't working and had been inconveniencing me quite bit, sometimes I have to try and load pages several times and then it start working and stops
Data speed can be slower depending on location and conditions at the time.
Maybe try to manually select 3G network, instead of LTE or auto. LTE speeds with Public mobile is capped to 3Mbps, while 3G network is not capped and many customers can get higher speeds. Will lose the LTE latency, but data speeds might be higher.
@Neil_2900 Not sure if it is a phone issue or network.
Have you try your SIM on another phone and see a much faster speed in the same place?
Have you try to use sim card from another provider in the same place and how the speed look like?
With your PM SIM, do you see the same slowness in different area?
You can try a Network Reset and see if it helps
If it still not working well, I think you still need to try PM sim in a different phone or try a different sim in this phone , and try this phone with a PM sim in different area to try to pin point if it is a phone issue or network