Hi Touggourt,
We currently use an SMTP SMS service but previously we have also used an App called Pushover which worked pretty well. The only downside is that you require it to be installed on each device but I seem to recall that the one time cost wasn't that much but they also provided a free trial to see if it was appropriate for what you need it for.
There's also this guide that may help
Sending Alerts to Mobile Phone using Pushover from HTTP.OutboundAdapter | IDC

One of the best communities out there, there's always someone that can help.

This is really useful, thank you.
I often have to look in the Community forum when it comes to handling dates and times.