Job always calls me on my days off?

I work in a retail store as a part time employee. I've been at my job for almost a year now. I work roughly 2-4 days a week depending on the time of year. (Holidays are when I work the most). I currently make minimum wage per hour.

My problem is that almost every single week, my job calls me on my days off to try and get me to come work. 90% of the time I go in for them. I understand retail is unpredictable and can get unexpectedly crazy, but bothering me nearly every single week? It makes me feel used.

My boss has told me before that I'm the first person in her mind to call whenever they need someone and that the manager below her also would choose me first. It's flattering and nice to know they like me enough to be their "on call" girl...but at the same time I feel like I'm being used for their convenience.

This past week I had Saturday - Monday off so I planned a weekend out of town and here's how it went:

Saturday: Manager texted me asking me to come in. I texted back saying I'd be out of town for the weekend.

Sunday: Store called my phone 2 times and I didn't return the calls.

Monday: Store called my cell once and called my house once (and let it ring and ring and ring). I haven't returned it.

What am I supposed to do? Enough is enough. I love working there but if they like me so bad and want me all the time, then they should either promote me, give me some kind of raise, or schedule me for more days a week don't you think? I have a busy life outside of work so this is just adding so much more stress. Any input would be very appreciated.