What do I do it say no sim at top left side of my phone and won’t make calls

If it does not have a sim card, then it cannot make calls.

A sim card is what allows you to make calls.

To see if it has one and remove it follow the steps in the link I provided: Remove or switch the SIM card in your iPhone or iPad - Apple Support

If the sim tray is empty, then you need to contact the Cellular service provider you want to use to make calls with, and request they give you a sim card with your phone number and the service you are paying for with them.

Then it either actually has a sim card inside, or you were using a digital embedded Sim which somehow was turned off in Settings.

Either way you absolutely need to have some type of sim card in the phone to make cellular calls

Since you have not told us how you were making calls its hard to say what is happening.

If it is a Network / Carrier / SIM issue --> If you see 'invalid SIM' or 'no SIM' on your iPhone or iPad ...

Remove the sim card and clean the gold contacts on it and re-insert it.

See here: Remove or switch the SIM card in your iPhone or iPad - Apple Support

If that does not help, then you will need to contact your cellular / mobile service provider as the sim card may have failed.

See here: If you see No Service or Searching on your iPhone or iPad - Apple Support