Sampling etiquette

I have a 7 year old acapella from a well known house label that seemingly fits into a track I am working on. Should I just finish this unsigned track soundcloud and hope not to receive a negative letter from the label or artist. Should I contact them and expect to pay royalties? Should I just give credit to the sample wherever I post the song? Has anyone been through the process?br
Would a song with a questionable sample be eligible for MIX MY TRACK?

If you’re not selling it I don’t see that it’s a problem