Voluntold
It’s actually a recognised word, ‘voluntold’. It describes the occasion when someone else volunteers you for something, or when you’re told to volunteer without much leeway to say no.
I’ve used the word jokingly in my committee work, where we’re already there voluntarily, and there’s just another task someone needs to do. But the online corporate definitions refer to underlying negativity of the situation, and how it can be used in underhanded ways.
I hope that’s not as common as it might seem. Volunteering is a wonderful use of time, and it should be a positive experience, not under duress.