If I send my phone in for repair will I get another phone to use meanwhile my phone is getting fixed ?

Apple can issue a loaner phone if repair of the unit requires it be sent off site.

From

iPhone Service Answer Center - Apple Support

Can I get a loaner iPhone?

If you bring your iPhone to an Apple Store or an Apple Authorized Service Provider, we'll try to fix it during your appointment. Some iPhone repairs require precise calibration on specialized equipment. If we need to send your iPhone to an Apple Repair Center, we'll check to see if you can use a loaner while your iPhone gets repaired. A loaner iPhone is available for most repairs that are covered under the Apple Limited Warranty.

Our repair center will return your iPhone to your service location when your repaired iPhone is ready. When you pick up your iPhone, return the loaner to us in the same condition as it was when we lent it to you.

Se você for na assistência técnica você deixa o seu la e se eu não me engano você adquiri outro ou então você troca o se por um novo se estiver na garantia, alguma coisa assim..