Not a lawyer, but... If OP has first use in commerce that predates theirs they could start, or threaten to start, the paperwork to have the trademark tossed. I

Not a lawyer, but... If OP has first use in commerce that predates theirs they could start, or threaten to start, the paperwork to have the trademark tossed. If they see you are asking questions that aren't a response to bullying, but that would precede a legal an attack their trademark directly, they might find themselves on a different footing. Regardless, the possibility, I would think puts you in a better negotiating position if you're looking for an offer, or just want to make them go away. Seeing a lawyer is likely the way to go. Also, I notice you use the term "solicitor" which makes me think any US law-based answers are less likely to be grounded in reality for you, so add more than your usual pinch of salt to anything you see here, including what I wrote!