Iphone5 can not read sim card

my phone was working fine

and all of a sudden i realise there is no network

i restarted the phone but still no network

i checked from service provider and after a day they reported that sim card is rejected

so finally i got a new sim

i put this new sim back into my iphone5 but still the phone keep "searching"

i tried the sim in a diffrent mobile and the sim is working

any help??