Who called from 6828085321

I have been recieving calls twice everyday from this number 6828085321. They will not leave a message. Why do these people call numbers on Do Not Call list?

Silverleaf Timeshare sales. They are really annoying and persistent.
The numbers that have called me so far from the same company:
817-522-5885
817-617-4340
682-808-5315
866-804-8589
682-808-5319
888-325-6863
817-525-1024
800-351-0774
682-808-5321
817-617-4335

I got the same thing no message! I usually just block all the numbers that don't leave a message.