I've been using Amazon SNS for sending transactional SMS messages for the past 6 months and had lots of problems with delays and delivery failures for Brazilian phone numbers.
I've seen other people having similar problems months ago and Amazon never answered them on their support forum, so I'm now looking for better alternatives.
Problem is, time's really short, and we can't be testing services for comparison; I have to pick one and deploy it, and it "has to work." Twilio seems like a really good pick, but I was also asked to try to find a cheaper one if possible...
So, is there a transactional SMS sending service that's able to send messages internationally, but which is also known to have best-in-class deliverability in Brazilian territory?
Looking for suggestions from people who had those same needs, who have successfully deployed apps using a given service, and who have seen it work flawlessly in practice.