mobile

Hello,
A friend gave me a retail Samsung Galaxy A5 from a shop and i wanted to know if there is any possible way to make it a regular phone.
Everything's working actually except from the fact that it doesnt recognise any Sim Card and the Call app "that Green Phone image" that any android has it's missing.
So ita can be used as a "tablet" but not as a phone.

I tried routing the phone but it didnt worked.

Any ideas?

Will flashing a custom ROM solve the issue?

If so can you please give me the steps in doing so.....

Thank you.