How can I use the same phone number for two-factor SMS on multiple email users?

How can I use the same phone number for two-factor SMS on multiple email users?

I'm on the Standard package. I have three email addresses on my own-domain Zoho-hosted email. All three addresses are mine, and I'm after two-factor-authentication on all three. However, I don't have a separate phone number for each user (as they are all me!) but when I attempt to add that number to the second user I get the message " Number already exist in organization".

It seems rather silly that the same person cannot use two-factor on multiple addresses without taking out a separate phone number for each - is there a way around this (as I *must* use two-factor but cannot operate with this restriction and so would need to look into cancelling the service less than a day in)?