Try some follow up to the solicitors' superiors.
I had a huge problem with this recently after major hail storm tore up all the roofs in my neighborhood. Roof company vultures were out in force for a month. I got fed up and placed a big sign on my door. Worked for most, but not all solicitors. Here's what I did with the ones who obviously can't read/comprehend.
I had some idiot leave a flyer on my door despite the huge sign saying "No soliciting No trespassing and YES this means no placing flyers and other nonsense on my door" I found out the name of the company - from the flyer, obviously - called them and they said they contract out their door-to-door pestering to a company that specializes in such. Called that company, no answer. Google search found an email address. Emailed with my complaint, digital photo of the flyer and my sign, and instructions that if I was not contacted within 48 hours with an appropriately apologetic response I would forward my complaint to my local police department. Lady emailed me back within 8 hours, apologized profusely, said the person who worked my neighborhood that day would be reprimanded. Haven't had a flyer on my door since (even took down the sign).
Previous to that, I witnessed an idiot put flyer on my door (same sign was up); I was across the street. I told him very bluntly to get off my property and take his damn flyer with him. He came back 10 minutes later with two other guys in a pickup truck; one guy, acting like a supervisor, asked what the problem was. I explained the situation. He told me I didn't have to "be so rude about it" and that they weren't breaking any laws and had a right to put up flyers on people's doors
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. I told him he was dead wrong and demanded he get off my property. He said "what, you wanna go? why don't you step out onto the street, punk". I told him he was trespassing, in clear violation of a posted sign, and had mere seconds to get off my property before I called the cops. We stared each other down, him on the street next to his truck, me on my driveway. He finally figured out I was serious and they left (I had my hand in my front pocket firmly gripped on my S&W 638 J-frame). Went inside, called the number on the flyer, spoke to the owner, explained the situation, and told him if I ever saw either of these gentlemen in my neighborhood again, I would immediately call the police. He apologized profusely, told me he would personally handle it. Never saw them again.
Some people just don't get it until you show them you're serious.