Both speaking in tongues and prophecy are called "gifts" in 1 Corinthians 12. Both are called "signs" in 1 Corinthians 14. The two concepts do not oppose each other.
Again tongues is prophecy the unseen spiritual gift. The sign is called a sign. The prophecy is called prophecy. No such thing as a sign gift . You will not find those two words (sign gift) working as one.
What God calls separate the counterfeiter god of this world calls one. Turning things upside down taking away the understanding of God.... The father of lies MO. The oppositer, apposer .