If you already did the work for which  they had said they would match the contribution, and at the time you did the work, the matching provision was in place, they have to pay you the match; they may not retroactively alter the rules or compensation for work already done, and doing so is a breach of contract--the agreement, whether written or unwritten, pursuant to which you did the work.Going forward, they can announce that they are discontinuing the match as long as you don't have an in-effect written contract guarantying it to you--prospectively, they can alter your compensation or the terms under which you work. It's simply retroactively they cannot.