Troubleshooting my mobile internet, because no one can figure it out

[levi]

But this is only possible if the two are on seperate frequencies I'd logically assume?

Not as far as I know; O2 and EE both run 2G operations at 1800Mhz in this country. 2G supports multiple carriers on the same frequency just as it supports multiple handsets connected to the same operator at the same frequency. I think the same is true for 3G and 4G, although they achieve it in different ways.

But it does seem I'm wrong to call them all GSM technologies; 3 and 4G standards were set by the 3GPP, while the GSM association is merely a 'market representation partner' of the 3GPP, whatever that means exactly.