Who called from 310487598

Got this call today 4 times! no messages as well...
weird number which can't even call back to check...

did not answer call, have rec'd calls from this answer b/f, but do not answer b/c of 6 digit #.

did not answer call, have rec'd calls from this # b/f, but do not answer b/c of 6 digit #.

Received on cell phone,  I'm going to try and find out who this is.  This is ridiculous.  They shouldn't be allowed to get away with this.

I received multiple calls from this incomplete number for a year now.  I never answer since the number looks suspicious.  I tried unsuccessfully to file a complaint with the National Do Not Call Registry because one must have a complete number to proceed to the next step.  This is the message I got from the site:
You must have either the phone number or the name of the company that called you to submit a complaint. If you have this information, click Back and complete the previous page.

What should I do now?