COULD NOT CALL AFTER UPDATE to OS10.3.3

Hello Apple support,

I have an iPhone 5 been using for a while and now I could not use after I updated to

OS 10.3.3, when people called me they only heard voicemail no ringing at all, when

I call out I have to wait for 20 sec. to hear other phone to ring. I don't know what

when wrong ? Can I downgrade the OS or throw the apple phone away.

Please give me a real good advice Thank you very much.