Depending on how many customers you have and growth, you might be better off providing your own DDNS server using open source software.
We have deployed several dedicated DDNS servers for security companies; it is NOT our software. We are merely using Debian Linux, BIND DNS server and a
perl script and it works like a charm. We have over 1200 customers that are utilizing this service with no issues. Before, we had to rely on the services
of other DDNS providers being reliable, cost, support, and staying in business. Now that our DDNS server is in the Amazon cloud, we run into NO issues.
The only cost is the $49.99 a month for the amazon server.