I want to signup and get sim cards for 4 new lines but do not want service to start until next month? Is this possible?
When you say new lines are you referring to new phone numbers or are you porting numbers from another provider? Do you need 4 new phones too? Port numbers and brand new service is different.
If you don't want the service to start immediately you can still order the sim cards but do not activate on device until you are ready. Also, check out what beav posted.
Sidenote: have you checked the IMEIs in the Visible checker, to confirm that your phones will work on the Visble network?
Visible offers some iPhone users a free 15 day trial here: https://www.visible.com/free-trial/
A link to the IMEI checker is there too.