Now, the problem seems to be with the cell phone device that you have.
Because, if the sim card works fine in other devices at your home, then it cannot be at fault.
The reason your cell phone works fine at other locations is likely because the cell signals are more powerful at those locations ... and are weaker at your home. And so it is not able to catch those weak signals.
Now, the best way to confirm this is by using other sim cards of telstra (from your friends) and see result. If those sim cards dont work at your home either, then your phone is at fault and you need to return it to Samsung if its in warranty. Else buy a cell phone booster (google it or let me know).
If their sim cards work fine on your phone, then let me know
Feel free to ask any question or concern you may have. I will be glad to help you.
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