I hate how they're always asking

My husband and I share a phone (it's mine but he uses it) and his family is constanly texting and calling my phone asking him to pick up his siblings from school and to take them places it's seriously so annoying like I wouldn't mind doing it once a month but it's like every freaking week at least 3 times a week. I understand his parents work but their daughter that lives with them has a car why can't she do it -.- His mom cleans houses she can always go pick them up and leave them at their house and go back to work. 

they wanted him to pick them up from school today his sister used the excuse she had work but she only works part time and I know damn well she didn't have to work today, she had been bragging about a concert she was going to go to today. I know it's not her responsibility either but still like why bugg us ? It bugs me because to pick them up from school my husband makes me go with him since they're 9 and 8 and there's no parking so he makes me pick them up while he drives around and then comes back for us what really annoys me is thay they NEVER ONCE give my husband money  for gas -.- gas isn't free ! like seriously how hard is it to say "thanks for picking up the kids, here's 10 bucks" (at least) we don't ever get a simple thank you. They never even talk to us only when they need a favor. My husband needs to find a new job asap so they will quit bugging him and he needs to learn how to say no every once in a while. I hate going out of our way to do things for them, shit not my kids,not my problem. And btw ima get bashed for this, but we didn't pick them up today I hid the phone and my husband hasen't asked for it. They need to stop depending on their son that has a family and 2 kids of his own now.