This is a call to test your line as part of a number port process. I received these calls multiple times for an entire day and then they just stopped. Coincidently I was porting my number from Vonage to another provider. I contacted my new provider (who has excellent technical support) and the person who was actually handling my port informed me that the 1-216-672-6203 number who was calling me repeatedly and hanging up was part of a line test for the port process.
It continues. I have received 9 calls today from this number. Most ring one time and quit. However, call log does record them. I am fed up with whoever this is, and will do whatever it takes to put a stop to them.