"By the way: I've always received answers to my emails from PTSC in the last six years - maybe it's you or our attitude which is the problem."

I think this is unfair of you.

I have emailed the same polite question three times in 2 weeks to ir@ptsc.com:

"I am trying to make my travel plans for the next few months. Could you please tell me when and where the next Annual Meeting will be."

No answer. Not even "We don't know yet."