Hello, thank you for reporting this issue. We are aware that some carriers refuse SMSes containing a link. We made all possible countermeasures to prevent our SMSes to be marked as spam, but the situation is very dynamic and changes from country to country. It is actually impossible for us to secure 100% deliverability of SMS invitations. As of the moment we deliver SMSes on “best-effort” basis, same as our downstream providers.
To increase chance of successful invitation delivery we recommend to send the invitation to both sms and email contacts. We know it is sub-optimal solution but it is honestly the best we can do at the moment.
We will further investigate options for SMS APIs, but currently none of the providers we contacted is able to assure delivery of SMSes containing URLs.