My iPhone is not receiving any calls but I can make calls and receive and send texts messages. When someone tries to call it says my number is not reachable.

I had this issue too, Make sure the person calling you isn't in your blocked contacts.

My Family spent ages trying to work out why my Dads phone wasn't calling for some of us and then we realised it because some of us where in his blocked numbers. He doesn't know how it happened so maybe just check there

Not Reachable, Busy, Out of coverage area, Switched Off -- All these alerts are carrier-specific alerts. Contact your Carrier.

Meanwhile, remove the SIM and re-insert.