Hi, I am a complete novice to these forums, but thought this would be the best place to get some education and advice. (Thanks in advance). I bought an (admittedly cheap) gps tracker called a G11 https://www.aliexpress.com/i/1005001868408894.html and placed a  ONE "pay as you go" sim in tracker.  It worked fine for the 1st 4 days, tracked, responded to sms commands etc. but then all of a sudden has come offline.  I do not have access to the tracker right now and wondering if there is any way of getting it back online remotely.  I am pretty sure it is the sim as when I text it, it does not respond, and when called, it goes straight to voicemail, whereas before it rang.  The device is in suburban areas, so not out with signal range, and I have topped up sim incase it ran out of credit, but in a few days I would have very much doubt it. 

As I said, complete novice here, and hope I've given enough info- any advice is appreciated.