Smile and say Thanks
It's best not to argue or engage them at all.
Smile and say "thanks" "i'll think about that." . If they continue, keep smiling and say "thanks" again. "i'll give that some thought". If you keep smiling and saying thank you, repeating some variation on this, they will eventually grow tired. Or it won't bother you as much since you've figured out a way to handle it. Don't give them the power to get.