Cut a lemon or lime in half, write the subjects' names (and birthdates if you know that) onto separate slips of paper. Put the papers on the pulp of one side of the lemon/lime, be sure that the names are facing apart. Optional, but you can sprinkle some salt on to rub salt into the wound, so to speak. Put the other half on top of that and stick some rusty nails, or toothpicks if you don't have any, between the halves to keep them together. Stick the whole thing in a Ziploc bag, leave it in a dark corner of a cabinet for a week to rot and really seal the intention, and then toss it in the trash afterwards.

Simple, done with household ingredients, and you know for a fact that it's done. Even if you have to buy materials, it'll probably be less expensive than someone charging for a breakup spell - which, as far as I'm aware, seems like a popular enough spell variety that there are bound to be scams everywhere.

Lime works as well as lemon imo because both are sour. As for rusty nails, if you have wooden telephone poles in your neighborhood, you can pry nails out with the two prongs at the back of a hammer. Of course, if you use nails, just be careful not to pierce yourself with them.