SIM card problems

Ok so my old iphone5c broke and so I am using an old iphone4s (ik sucks right) anyway so my mom went to the AT&T store to activate my "new" phone and they switched the sim but now it doesn't work. It doesn't say no service and it doesn't say like 4g or LTE it just says searching… does that mean it's like loading or is it just not working???