Let me get one thing off my chest: I am really peeved with software vendors who charge for technical support - even when you are reporting a bug!
There are different business models out there, and technical support options might vary. Some people might offer only one tier of technical support, and usually it is free. Others offer both free and paid tech support.
But whatever the case, there should be a way for you to dialog with a vendor to report a suspected bug - and to hear back from them about it.
Do not blindly trust what a vendor promises. Check it out for yourself (most vendors will provide free tech support for prospective clients using a trial account):
Ask specific questions and see how good the answers are (specific to your question or following the standard template).
How quickly do they get back to you, compared to what is promised?