No such thing as a dumb question :)
تلفون means telephone
تلفوني means my telephone
تلفونك means your (sgl.) telephone
To expand one what Giorgia has said:
ي suffix means "my"
ك suffix means "your" (singular): كَ (ka) is for masculine, and كِ (ki) is for feminine.
Second-person plural all-male or mixed gender: تلفونكُم
Second-person plural all-female:تلفونكُنَّ
Third-person plural all-male or mixed gender: تلفونهُم
Third-person plural all-female: تلفونهُنَّ