Hi Marc-Allen55883!

I am sorry to hear you are having issues with SMS reminder deliverability. I can certainly understand that being frustrating for both your hosts and invitees!

We use long code for internal numbers, and in general, long codes have less deliverability internationally. Some wireless carriers may filter it out, and some countries are more strict on that than others – for example Canada has very strict guidelines. Due to filtering limitations, Twilio may be unable to deliver messages to Indian or Canadian phone numbers. More details about filtering here and in the troubleshooting steps below.

In certain countries (Afghanistan, Benin, Cameroon, Chad, Congo, Democratic Republic of the Congo, Ivory Coast, Gabon, Ghana, Guinea, Guinea-Bissau, Kenya, Liberia, Madagascar, Malawi, Niger, Nigeria, Rwanda, South Sudan, Sudan, Tanzania, Uganda, Yemen, Zambia) SMS messages must be sent from an Alphanumeric Sender ID (i.e. CALENDLY) rather than an American phone number. This is to comply with carrier regulations.

Additionally, Twilio has stopped supporting SMS delivery to Russia or phone numbers with (+7) area codes.

Further, there is no ability to send SMS reminders via a custom number through Calendly. The number used for delivering reminders is based on country regulations and system capabilities and varies based on international location. We are not able to customize the name or number the reminders are delivered from.

If you need additional control over this functionality, you might consider using something like our Zapier integration to accomplish this, connecting Calendly with an external SMS service.

I do see that you reached out to our support team about a similar matter and that you were given information to look into regarding carrier filtering. Are you having new issues in regards to SMS reminder deliverability, or is this in regards to the same matter? Thanks for letting us know and your continued patience - and for participating in our community!