Is there a custom rom or root I can use on my Samsung S5 (AT&T) for use in UK on (3) network?

[T0mmiB0i]

Samsung s5 at&t for use in UK on (3) network

Hi, I have recently purchased a phone from the us that was on the at&t network, I have since got back and found out that my phones frequency of 4g is not the same as the frequency of 4g for my network. I like my contract and do not want to have to change carriers is there anyway I can install a custom rom/ root my s5 to allow usage on my network?

Thanks allot,

Tom