What makes you think all phones have unique numbers? Some have no direct dial numbers.
As for each device getting a unique IP address this is somewhat in the spec for EUI-64 IPv6 address. Your IP is based on your interfaces MAC address but this becomes a privacy nightmare.
If the MAC address’s of the wifi chip in your phone is 1122.3344.5566 your IPv6 address at home can be 2001:0db8:0000:00000:1122:33ff:fe44:5566 but when at work your address may be 2001:db8:1000:0000:1122:33ff:fe44:5566. No matter where you connect to the last 4 sections of the address is the same and companies will use that as one of the data points of your digital profile.