iPhone 7 repair

I have an iPhone 7 128gb product red that has been giving me a “No Service” issue. I mailed it to Apple yesterday but I am wondering how long this is gonna take them to repair it. I believe it’s covered under a repair program because a lot of people have had the same issue as me. Anyways, I was just wondering how long the repair would take because I’m now using an iPhone 6s that shuts off sometimes.