How to regain access to Telegram channel? Lost admin.

Hey fam,

we used to run an active TG channel for our startup. However people on the team changed and we can't restore access. It's our brand, but no one of the active team members has admin rights and we don't know who had.
We DM'd telegram team, messaged support, messaged them via X - no luck.

Any suggestions what to do?
It's not a massive channel, but it has our brand name and 600 users.