Fix no service iPhone 4 any tips?

Ok so I brought a iPhone from this person who was selling it so I brought it when I got home an tried all sims non of them worked. So when I click on settings then phone it says the phone number in the iPhone but still says no service. Its also jailbreaks this iPhone. So can some 1 please tell me some tips on how I can get well repair the no service. An last night it got froze shud I restore it but I'm thinking not to restore it because itll take the jailbreak n I might need it any ideas please

Its locked to a carrier… You need the original sim card to use it