Must have been a miscommunication with the customer service. But in all honesty I did pay to have it sent and they paid for the return.
This has been my experience also. I had to send my 4-16x50 PST back twice for a reticle problem and illumination being broke (would go to brightest setting on all "off" spots of the dial). Both times I paid for shipping but never asked for a shipping label.
The second time was a couple of months ago. I filled out their form, went to the post office, sent it out, got back and there was the form! The post office was going to be closed before I could get there so I called Vortex. Immediately got a very nice CS lady and explained the situation. I read her all the stuff on the form as she typed it up on her end. She said it'll be waiting for when my scope came in and they'll get right on it. I had it in less than a week fixed and ready to go!
About the only thing that I would do differently than the OP would be not to try different rings and rifles. If you're confident in the rifle, the mount, and your abilities to properly mount an optic, don't throw good money after bad. Trust yourself, send it back, and let them figure it out.