UNWANTED car STICKER adds - WITHOUT approval...?

ok so i work for a company that shares a block with 8 different business's... a business ACROSS the street finds the need to put their company advertisements (look like a BIG sticky note) on our car windows 5 out of 7 days of EVERY week!!!! sometimes i come out to my car and have them on BOTH the driver AND penger windows!!! the other day i had my car detailed... went to work the next day... and yeah.. sticker on the window.. i pulled it off and yet AGAIN it left a small but nasty sticky crap on my window...i cant stand it anymore!!! PLUS im an earthy person... and when i leave work 75% of the stickers AT LEAST are laying littered in the parking lot which is a HUGE concern of mine!!! how do i stop this?! my car IS being vandalized!! what actions do i take?! do i go to the city or what??!