1. Make sure that they are dialing the correct number. This includes if they should or shouldn't dial the area code, a 9, etc...
   
   
2. Are they hearing a voice? Not hearing a modem tone? Make sure that the POP isn't having any sort of issues.
   
   
3. If they hear a connection sound, try R&Ring the modem, updating drivers, inits, ATZX0(reset and blind dial) as an init, etc...
   
   

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