Can flight attendants send text messages on their mobile phones or something?

Not in principle. Actually, it depends on whether there is a signal. There is no signal when flying at normal altitude. It doesn't matter if you secretly send text messages when there is a signal. The captain will call to order food when he is about to land. The signal of the mobile phone will not have any influence on the plane.

Wages vary according to different companies. The southeast coast and the west can be much worse, and they are generally calculated by the hour like pilots.