Ignoring just for a moment your view that the speaking of tongues has ceased, I need to know something more about the interpretation of tongues, namely – Was it OK for the speaker of tongues to interpret the tongues himself / herself? The Bible says so; but I am unable to see what the purpose of speaking in tongues would have been at all if the speaker was also the one to interpret. Why then not speak the interpretation straight out, without the tongues?
The reason that “speaking in tongues” was employed in the first place (first in the New Testament in Acts 2) was to communicate effectively with audiences whose languages differed from the native language of the speakers (Acts 2:6-11). While all those in Acts 2 may have known a common language besides the languages native to the parts of the world in which they were living respectively, the relatively uneducated apostles of Christ speaking in those respective native languages caught the attention of the masses and validated that it was God’s Word that was preached that fateful day. However, when an individual, miraculously assisted preacher stood before an audience in which more than one language was represented in that audience, it was necessary for the Gospel to be preached in one of those languages and then re-preached or interpreted in the additional language also represented in the audience. Someone besides the preacher if someone were available who knew both languages could do the interpreting for a second language present while the preacher preached, paused, preached, etc. If, though, only the preacher present knew both of the languages represented in his audience, he would have to preach in the one language and re-preach or interpret the Gospel message for the additional language present; that is how one might find himself in biblical times preaching and interpreting the same Gospel message.
The same circumstance without miraculous assistance continues today, especially respecting foreign evangelism. A preacher friend of mine goes to India for several weeks annually and preaches the Gospel widely there. Since he is unfamiliar with the various languages spoken in India, he uses an interpreter to translate his preaching for the native people. On one occasion, my preacher friend noticed that it was taking a lot longer for his interpreter to translate the Gospel message as he paused his preaching. Therefore, he sought assurances that his interpreter was just interpreting and not adding to what he was preaching, and he wanted to know why it was taking so long to interpret. It happened in that there were two different languages represented in that particular audience. The interpreter had to interpret the message twice every time the preacher paused to permit the interpreter to translate. So, counting the English language in which the preacher was speaking, three languages were present and spoken or interpreted on that occasion.