Can someone can use an iPhone contact number to harass someone else?

Nope, no one can hack your contacts to impersonate a call. This is different from spoofing where the caller can change the Caller ID number that appears and will bring up that contact. I would consider that a prank. Have you reviewed the contact information for that person? Go to the Recent Call list and tap the info button next to that person to bring up the Contact card. There may be several numbers associated with that contact card and anyone one of them will bring up that person when a call is made.

In addition, if that person changes their card info on their device to add a different number, you get the option to update that information and if you chose to update, the information from them will be updated on the Contact on your phone.

WTP5 wrote:

I received a call from a known contact in my iPhone today and it was not the person assigned to that contact. Was I being pranked or can someone piggyback a number (hack) and use it to call me? I will pursue further investigation but I am a little concerned someone can use a contact number to harass someone else. Thanks

[Re-Titled by Moderator]

Yes any number can be spoofed, there isn't much you can do about it until the scammers moves on to another number.