Iphone 5 wifi doesn't work on 2.4 GHz network

It works completely fine on 5GHZ networks but can only get speeds of <1MB on 2.4GHz networks while all my other devices work fine. I've tried this on many routers with the same result.

Other people's iphones work fine, I've put them side by side and ran a speed test. The result of this is their iphone gets speeds of 15-20 MB when mine gets 0.5MB.

I've contacted apple and someone gave me their phone number to call after discussing the issue with them. I left a message days ago and haven't heard from the Apple employee.

I'm not sure what the issue or solution is at this point. Apple hasn't been very helpful at all

I've tried everything from router settings, to iphone restores, to clearing network settings, etc