Something like this filtering link for this condition
https://sobr.crm-onebox.com/admin/shop/report/event/?evtype=sms&direction=ou... =&content=&durationfrom=&durationto=&line=&filtercontactid%5B%5D=17&page=&mailbox=
if there is at least 1 message under such conditions, a new one will not be sent
You can check by phone number, but if you have this number used to send in several processes with the same action, it will not work quite correctly.
If you still need to check by number, not taking into account the user - the cost of revision is 1 hour