Hello,
My name is Sam and i'm a composer and music producer, with 7 years of experience.
I've also worked with sound restoration and sound enhancement.
To remove the vocals of a song (if you are not disposed to write the instrumental again) is difficult but not impossible. It depends by its structure and how the song was realised.
If your song allows to do what you're asking for, it won't take more than few hours, so you shouldn't have to pay more than 15 $ for this service.
Please contact me and send me your song so i will be able to tell you more about it. I will be at your disposal!
Bye,
Sam.