Acts 2:4And they were all filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance.
Acts 2:6 Now when this was noised abroad, the multitude came together, and were confounded, because that every man heard them speak in his own language.
They were speaking in tongues and tongues was another language.
I have heard churches speak in tongues...it is gibberish, not a real language. There was no one to interpret as commanded in 1 Corinthians 14:27, was there in your church?
So, your church can not claim all the signs in Mark 16:17-18...some does not fulfill the text...so Mark 16:16 is misapplied.
No doubt the church speaks their own language...that is not speaking in another's language.
Fact is, no church can claim all these signs because Mark 16:16 was given only to Peter and the disciples and was not yet fulfilled...their "great commission" was interrupted with this dispensation of grace and will resume in the future tribulation....trying to apply this today, to the church in this dispensation, is at best error.
When it comes to tongues as Charismatics understand them the jury is out as far as I am concerned. There seem to be arguments in both directions.
However Acts 2:2-6 doesn't actually say the apostles spoke other languages.
Acts 2:4 says they spoke "other tongues, as the Spirit gave them utterance".
Whereas Acts 2:6 says "each one heard them speaking in his own language".
The miracle could be that they heard them speaking their own language even though they weren't.
Tongues in Acts 2:4 is G1100 - glossa
Whereas languages in Acts 2:6 is two words G1268 & G2980, literally vernacular speaking.