The simple answer is no. There are other technologies that can be used such as cellular and Internet that can replace a phone line. If you have a VOIP or similar non-traditional line, it probably will result in problems communicating. If you switched at some point, you should be making sure that your system does regular tests of communication and that you do your part and test your system at least once a month.
By the way, if you are wondering what POTS stands for, it is Plain Old Telephone Service!