We're so confused!

Tonight on our way home from small group, Dave tried to call the boys on his cell phone to let them know we were on our way home and to be ready for bed. When he dialed our home number he didn't get anyone here, he got another residence, so he decided to try again....same thing. The third time he very carefully punched our home number into his keypad...same thing! The man on the other end was a little impatient, and I guess rightfully so. Dave told him what number he was dialing and asked what the number of the residence was. Very strangely it turned out to be an OLD cell phone number of Dave's. ??? It was a slow ride home due to a lot of snowfall and slippery roads, but we finally made it. Later, after the kids were in bed I realized that our internet connection didn't work on either computer, so Dave went to the basement to reset the modem and the router. I was then able to connect to the internet, and almost immediately got a phone call from our telephone company. Dave's sister had evidently tried to call us 5 times and had gotten this other residence instead, so she called our telephone company to report that some lines must be crossed.
This is the reason that we kept getting the other residence...A LONG time ago, Dave gave the phone company his cell number as a number that a phone call would be forwarded to if our telephone was out of order. Evidently he never gave his new cell number, therefore this poor family has been getting a bunch of phone calls intended for us. (I called a couple of times a few weeks ago on my way to work and got this other family too)