There is an old tactic salespeople were taught called the breakup letter. The idea is that when a prospect won’t engage with you or goes dark, you send them an email or leave a voicemail message informing them that you are going to “close their file,” or some such thing. The idea is that threatening to disengage is going to cause your prospect to respond to you.
The Problem with Ultimatums
To issue an ultimatum, there is a prerequisite that allows it to be effective. That prerequisite is that the person you are threatening needs you more than you need them. This deserves a little exploration.
Do you believe that your prospective client needs you more than you need them? When you walked into your office was there a line of clients waiting outside to buy from you?
Are there no alternatives to what you do that your prospective client could easily choose instead of working with you? Is it possible that they need only open their inbox to find the name and contact information of someone who looks and sounds a lot like you with whom they can work on the very same thing you sell?
The problem with ultimatums is that they are easily accepted. Your prospective client suffers no harm from agreeing to your offer to go away. You, on the other hand, do suffer.
Taking Your Toys and Going Home
There are certain strategies that I have outlined here, mostly under leadership. The poor strategies for getting what you want include things like force, coercion, and manipulation. These are the choices of the weak, who struggle because they lack more effective ways to get what they want and resort to strategies that damage relationships. Approaching relationships as if they are only a means to your end is how you ensure you have very few and likely unhealthy relationships.
Trying to force someone to give you your way is childish. It is akin to threatening to take your toys and go home. It is also an indication that you are not a peer, that you are not consultative, and that you lack better strategies to get what you want or need, projecting the kind of partner you might end up being.
You are better off here using a more professional approach, one that serves you and your client. Make a better choice.