Shortcodes are really simple and easy to use for your end user. Only 4 digits to remember. However, because they only have 4 digits, the number of possible shortcodes is limited. That's why multiple customers can share one shortcode.
Luckily, RingRing handles all that for you and you don't have to think about that too much. However, it is important to understand how this works, to construct your message.
Let's take the example of a contest on shortcode 6464. Company A has a contest where you can win a car if you answer "What is the capital of France:
At the same time, on the same shortcode, company B also has a contest where you can win a trip to Hawai, if you answer "Who played in Die Hard:
A: Bruce Willis
B: John Goodman
C: Jean Claude Vandamme
Now, shortcode 6464 is getting these responses:
"A: Bruce Willis"
"Hey, did you see that Bruce Willis movie yesterday? It was awesome!"
We now have no idea which answer is for which contest. As a human, we can probably deduct that the third answer is for the second contest and that the last answer has nothing to do with any contest, but computers are relatively "dumb".
To resolve this, you use a keyword, to identify your contest. So company A should ask their customers to answer the contest with "CAPITAL B" and company B should use something like "TRIP A" or "TRIP Bruce Willis". All other answers in the incorrect format, will be considered incorrect, even though the answer itself might have been the correct one. So it is important to instruct your end user to use the correct format.
When an end user is responding to a message that you sent out, our system does know who the message is meant for, so they don't need to use a keyword. We do encourage you to always identify yourself when sending a message. So instead of sending "your appointment has been cancelled", send "Your appointment has been cancelled. Kind regards, Dr Smith".
A last thing to consider is that if a reply from a shortcode is necessary, it will be a general message, for all customers on that shortcode. Let's take the example of the contest again. If an end user responds to your contest in the incorrect format, the shortcode cannot know for which contest he/she is sending a message and will return a general message like "This contest has expired or your answer was incorrect or in the wrong format".
I hope this clarifies the concept of a shared shortcode for you. If you have any other questions, please don't hesitate to contact us at firstname.lastname@example.org