99.5% of all the advice TUGGERS on this blog have opinined on is SPOT ON. I would just like to add a few thoughts. I lived in Mexico a few years ago and understand the customs and have some knowledge of their jurisprudence and banking nuances which are very different. A number of years ago, several important consumer protection laws were enacted to help us foreigners extract ourselves from business deals and contracts in Mexico. By far, most Americans fall victim to the "timeshare" pitch, which in Mexico, are all "Rite To Use" contracts for 25 to 30 years with succession rights. But, more fundamentally, most if not all timeshares purchases in modern times are extraordinarily bad business deals, why would you buy anything in the first place? You can book most resorts (ask any guest staying there who did) for less than the maintenance fees you would pay even if the resort were given to you gratis. Of course there are some exceptions but the are not worth the premium one would need to pay.
Overall, the rescission process is straightforward and keep all original records. Get verification the money withdrawn was returned within 48 hours.
One last rule, never make any business decisions under duress. When you are on vacation, because of the nice weather, adult beverages, relaxed and elated mood, sets you up for making mistakes. You drop your guard and vulnerable. A simple analogy makes the point. You go on vacation and walk past a car dealership. You may or may not be interested in buying a new car, but you are enticed inside because the salesperson comes outside with a cocktail and says if you come in, I'll give you a gift you can use on your vacation. Well, you take the bait and enter. You sit down and the salesperson tells you about the amazing product and the special offer only available today. He then gives you a selling price. Would you buy the car based on this sales pitch? Hardly. What is amazing is that we would never buy a car going on vacation in an unfamiliar place without knowing what the market price is. Yet, in this example, this is what people do because the fail to realize that you must know the value of what you're buying.
Thank goodness you realized you made a mistake. Reach out to TUGGERS for further advice. We are here to help people avoid mistakes and enjoy hassle free vacationing.