If you have a written contract, then you could sue the vendor for breach of the implied covenant of good faith, and show that the vendor continuously tried to deprive you of the benefit of the bargain.
If you have no written contract, then you would have to prove that such an implied agreement for you to have exclusivity in your locale existed, and then prove breach of implied covenant. But, it would be incredibly difficult without something in writing.
Other than that, as long as the vendor does not act in a manner that reduces competition in the market for similar products, you have no recourse, based on your alleged facts.
Hope this helps.
Terms and Conditions: By your continuing in this conversation with me, or by your clicking “Accept”, you are expressly agreeing to all of the following: (1) our communication is for entertainment purposes only; (2) you are not consulting me in my professional capacity as an attorney; (3) you do not seek to establish an attorney-client relationship with me, nor do I with you; (4) you will not rely on anything I say and you will obtain appropriate legal counsel via a traditional/office consultation with an attorney licensed to practice in the jurisdiction where your legal issue arises (and you may not use our communication to avoid taxpayer penalties imposed by the U.S. Dept. of Treasury); (5) by communicating with me in this public forum you are irrevocably waiving any right to privacy, confidentiality and attorney-client privilege concerning the matters discussed. You further separately declare that any payment made by you is not consideration for this contract, nor offered for any services rendered by me on your behalf, but rather is made in genuine admiration and respect for my desire to help others. If you do not agree with these terms and conditions, then you must advise me immediately.