why isn’t my iphone 7 plus working ?

my mic is broken . i can’t hear videos . when i call someone they can’t hear me and i can’t hear them. when i call on facetime it goes straight to failed or unavailble even if they answer the call. when i call on phone the facetime button is grayed /blurred out. and sometimes the add call button. if you know what i can do please tell me. my friend is also having the same problem with the same phone