Lying To Audacious People
There is another way that is a polite and clear No. You let people know that by no means no. Lying is not allowed here. If the do not respect your wish you need not to respect their insistence.
The principle derived from the example is that we cannot commit a sin to please someone. To tell a lie is a sin. You cannot lie. no matter whether one is displeased or not. Find a way to decline politely in such matters without telling a lie.