If a customer (or a potential one) shows up with a request that is not in line with your procedures, processes, habits, or even product or service, the generous thing to do is to make an exception.
If that requests gets asked more and more, than you have two options.
Change your procedures, processes, habits, product or service to incorporate the request. You invest time and energy in making a change, as you see that the customers that are asking for it are the ones you want to serve.
Or you say, “thanks, but that’s not what we do.” Not all customers are your customers after all, so it is ok to decide that those asking for that additional feature are not the ones you want to serve.
There’s actually a third option, one you should avoid, the worst one. Not do anything. Keep getting the request, leaving its satisfaction to the moment, juggling about without any clear indication if that’s something that belongs to you or not.
This wastes your time and that of your customers, and time is not something anybody has to spare.