INFO. Are your parents members of the church? Have you absolutely decided you are done with the church?

Full disclosure, I'm an active member of the Church of Jesus Christ of Latter-day Saints.

First, you need to understand how the system works. It's all digital now, so, it's totally possible your phone number ended up on your record. Nothing diabolical, but it may have been added prior to you going inactive. Anyone in your ward/stake would have access to this.

It sounds like your familiar enough with the church to know one of its main focuses is missionary work. That includes the reactivation of inactive members; last I knew, you are considered inactive after a month or so of no attendance at church (don't hold me to that because I'm not 100% sure on that). So the fact you have been less active for years, and inactive for months, it would be reasonable to assume you have landed on the wards missionary efforts to reach out to you. And yes, wards typically end up with very enthusiastic ward missionaries.

I get the whole singles ward thing and the stigma it carries. I view its purpose as being a ward geared to people that are in theory in similar places in their life, age, location, education, careers, and yes relationship status (married vs not). I'm going to take a guess and say when your name came up in discussions on what they could do to help you, they may believe that your lack of attendance was due to not being around those similar to you, hence encouraging you towards a singles ward.

If you don't want them to bother you, but, are open to return some time in the future, just explain that to them. Just tell them your not there now, might be in the future, but that they are just pushing you further away.

If you are 100% done, and you are 100% sure you will never go back, you can arrange that. It would probably require a discussion with your bishop. But, if you ever chose to return in the future, you'd basically need to start from 0.