A potential client wants me to fix a critical bug on their app. She wants us to book a call so she can explain the issue to me.

Because so many clients have wasted my time in the past, I want to charge her some $$$ for the call. However, if the gig goes through, it’ll be deducted from her bill.

Does this make any sense?

Sounds reasonable at first.

But keep in mind, they could do the same thing with you. For them, you're just an exchangeable ressource and they don't want to waste any time, either.

On the other hand, one could argue that she's going to be paid to call you anyways, while you aren't guranteed to get your time paid and you may make minus because of this call.

I can understand both sides tbh.

@nitwhiz This. Both sides.

The client really needs to document the issue with the process involved and screen grabs if applicable and notes. A verbal communication assumes you have existing knowledge of the app. Without documentation you are destined to fail and the conversation will be used against you. A paper trail is the way to go, you can respond in writing with a proper estimate. There is no confusion and you will likely be paid. Also you need to have a signed contract for the work. If they are not prepared to work in a professional manner FUCK THEM!