No service Iphone 3gs

Used redsnow to hacktivate 3gs running 6.1.6 baseband 6.15 old boot rom cydia installed with ultyrasnow but getting no service. when I try to downgrade the baseband I get an error. I am not sure if I should install the ipad baseband as there is a warning and my serial number is higher than what they say is allowed. Is it safe to install the ipad baseband?