If you want a job you can find one, assuming you are able bodied and minded. It may not be your dream job (in fact it almost certainly won't be) but you can find one. If you're not in the middle of nowhere, I can almost guarantee a retail store is hiring for overnight stocking near you. A resume is probably nice to have, but certainly not a requirement. The turnover is so high in stocking positions that they often take whatever they can get. (I realize the thread isn't about this, but you gave us some info and you will likely find yourself hungry and cold if your mom was truly your only means of shelter and food).
As for your phone, there are government funded programs for mobile phones. You mentioned you needed a phone, you can almost certainly get one for free with a couple hundred minutes (maybe even no limit) per month. You will have to look into that, but if what you are worried is not having a phone at all, don't worry about it. It won't be an iPhone, but it will be a phone you can use for emergencies, and of course as means of being contacted for that job interview. Of course there are also means of obtaining food credits and even housing, but that varies by state as well.
I don't think AT&T will shut down your service immediately. Some months ago we got our new chip and pin cards and I forget auto pay was on the old one. It took two months before AT&T sent me anything regarding "please pay us now". They didn't threaten to terminate. It is a "business" account that has been up to date completely for 5+ years though.
You can backup your iPhone tot he cloud. That will 'forever' backup all texts and everything. This way, whatever may happen to your phone, if and when you get a replacement iphone everything will be there for you. You can also backup to your computer for some added redundancy.
Best of luck. I know this is a terrible time for you right now.