I know someone who did and it worked for a while until the provider contacted them to ask about the unusually high activity. They explained the situation, but since their package was a B2C package and they were using it for their company, the provider told them to either stop doing it or switch to a B2B package. There was no unlimited text B2B package available at the time and all of them were quite a bit more expensive than B2C. The latter has changed since, but I'm not sure about the rest.
Standard SMS plans usually have a human-typing-in-a-keyboard rate limit, around a handful per minute - you can manually try this, I've got blocked a couple of times by spamming a friend with "a", "b", "c"...
Were I work, we've implemented a couple of nation-wide general population surveys regarding non-communicable diseases (working with those countries health authorities, of course). For the actual surveys, we get SMPP contracts with the local telcos because of this limit (and to get a vanity shortcode, reverse billing...).
We started thinking it would also be cheaper, too (due to the scale pricing) - but the human time required for working out contracts with developing-world telcos for a project involving state actors can easily counter that.
The throttling is something we need to take into account for the tiny-scale pre-tests we ran (while working out the contract) using an SMS Gateway App[0] we've built, similar to the one from this thread. The main difference is ours uses a queue-based protocol to exchange messages with a controlling server.
Yes, most ordinary service contracts are "unlimited" for personal use.
A "person" can't reasonably compose and send more than 3 or 4 messages per minute on average. Send "too many" as defined by the carrier and you will likely be cut off.
I once sent 10k sms messages per month for about a year before my plan got cancelled. The plan officially allowed for unlimited sms. It was about 50$ per month, which was much cheaper than 0.1$ per message at Twilio (in Europe).
I received the bill at the end of the month stating the timestamp and recipient of every message. The PDF was regularly around 100 pages long.
What does throttled mean in SMS context? I can see why internet would need to be throttled but SMS is very infrequent and low data for it to be required to be throttled.
Im guessing "unlimited" sms, is also similar to "unlimited internet", you start sending more than a 1000 sms messages a day you might get throttled?