Wi-fi Card Upgrade

I've recently switched to a cheaper Internet Service Provider, one of the reasons being that I would get three times the speed. Instead, my speed has gone down, and now I can't even access my bank on my mobile phone when I'm in the house. I phoned the ISP, and they told me that the Wi-Fi card in my PC was only 2.4 ghz, whereas it should be 5 ghz. I can't understand this, because accessing the app on my phone shouldn't be affected by the Wi-Fi card that's in my PC, I wouldn't have thought? Can anyone advise on this please?

 

It shouldn't. You seem to be finding out exactly why they are cheaper.

 

Exactly what I was thinking!