I have recently swapped to a giff gaff sim only on my galaxy note 2. Its been workin fine but recently at work my mobile data wont work when set to both WCDMA/GSM. I get a little "g" in the corner and its that slow its unusable. When i swap it to WCDMA it still works slow but usable with a "H+" symbol on phone.why does my phone pick up the worst of the 2 networks GSM when its set to choose the fastest?

Probably a better idea to ask this on the GiffGaff help forum.

 

It might be the first network has got a stronger signal, but is getting a lot of interference that slows it to a crawl.due to packet-loss issues.