Money solicitation scams are common and so many states have specific rules controlling how to ask for money donations. A Texas-licensed attorney would have advise you on how to comply with that state's rules. In addition, it would be false advertising to state "Last chance" if, in fact, there will be subsequent opportunities to donate.
The above response is general information ONLY and is not legal advice, does not form an attorney-client relationship, and should NOT be relied upon to take or refrain from taking any action. I am not your attorney. You should seek the advice of competent counsel before taking any action related to your inquiry.
You really don't get us enough to go on, do you? It makes no sense to simply post a notice saying "last chance to send $50" (or whatever amount) unless it is associated with some goods or services or prize or other item. I do not think you are being honest with us so, being a Texas lawyer, I prefer not to answer you except to say you are almost certainly violating Texas law
I am not your lawyer and you are not my client. Free advice here is without recourse and any reliance thereupon is at your sole risk. This is done without compensation as a free public service. I am licensed in IL, MO, TX and I am a Reg. Pat. Atty. so advice in any other jurisdiction is strictly general advice and should be confirmed with an attorney licensed in that jurisdiction.