I hope i will not do a mess in scratch servers, sorry if it happens!
So, you may ask urself "But how does it work???" well: when you start the project your number is [Days since 2000] joined to [random number 000-100]. and when you call somone the system checks if theres anybody online with the number you called to, then it sends a signal to the one you called to and BOOM! a telephone.