I have a link in the below way and unable to pass the values to the link

http://myweb.com/cgi-bin/display_tic...3&carrier=AT&T ----> unable to parse data

Actually AT&T is the actual value but it is treater AT at a string and I am unable to retrieve the data from the link.
I have tried all the below ways but none of them are working ...

http://myweb.com/cgi-bin/display_ticket.cgi?Field7=123&carrier="AT&T" ---> not working
http://myweb.com/cgi-bin/display_tic...9;carrier=AT&T' ---> not working
http://myweb.com/cgi-bin/display_tic...rier='AT&T' ---> not working

But if I pass any simple string it works fine.

http://myweb.com/cgi-bin/display_tic...carrier=sprint -----> works fine.

Could anyone please let me know how to proceed further .....