This feature supplies you with a permanent long number, from which you can send and receive SMS messages. Similar in operation to the SRS (see here), the service allows customers to send SMS and receive SMS into their SMS portal. This service carries an additional rental charge for each DIN you have on your account.
Uses 1 credit per SMS sent, rather than 1.5 credit with the SRS system.
Multiple numbers can be used on the same account, allowing each number to be used for different campaigns, services etc.
If sending large numbers of 2-way SMS messages, will work out cheaper than using the SRS system.
Expensive if only sending a few 2-way SMS messages