Hilchos Lashon Hara chapter 10, section 12

This is even more true if the person did not harm you, but only failed to do you a favor he should have done, such as a loan, charity, or hosting you.

If you tell about this in order to put him down, it is complete lashon hara, as we wrote above (5:1). You also transgress other negative commandments, as explained there.

Many people stumble in this. If they are not welcomed well in a town, they speak badly about the important people there for not helping them.

It is even worse, and a terrible sin, to speak badly about the whole town. Lashon hara applies when speaking about one person, and also when speaking about a whole Torah-observant town.