@Sean
I understand how this could be a bit confusing. The reason one phone number can't be assigned to two or more Assistants is to ensure that each Assistant has a unique point of contact. This helps in routing calls correctly and avoiding any potential conflicts or confusion that could arise from multiple Assistants trying to handle the same incoming call.
The use of checkboxes in the user interface might indeed be misleading if multiple selections are not permitted. It would be more appropriate to use radio buttons to indicate that only one option can be selected. Your feedback is valuable, and I'll make sure to pass it on to our development team to consider improving the user interface for a better user experience. If you have any more questions or need further assistance, feel free to ask!