Hey there, . It's such a bummer to read that you're still experiencing issues with On Demand Activation on your Series 3.
I looked this error (409) up and it does look like our internal documents list resolution steps. A member of our tech team with account access should be able to refer to DOC-437039 and follow the steps next to that error number to resolve the issue. It does mention (under the resolution steps) that if you've purchased the watch somewhere other than T-Mobile, we'll need to manually activate the Apple DIGITS line for you. I know it sounds like you've reached out before, and definitely this is a busy time of year for many folks, but if you've got a few minutes to Contact Us and reference the document number above, we should be able to get this taken care of for you!