Well, I am happy to say after sending the C&D letter to Sonic and explaining how my extension payments (here in Ohio) should be applied to my principal balance---they AGREED! They deducted the amount of my extension payments and only charged me the bank charge of $20 AND are allowing me to make monthly payments with a money order.
With zip19 (aka Northwest...), they are still not providing me with a U.S. address just the Malta one. I did call their e-care centers and spoke to a nice rep. I asked him to provide me in writing were to send the legal amount owed. He was very nice and did send me via email the appropriate letter--I do have to send it via moneygram for a cost of $4.00.
Lastly, for mycashnow.com....they are sneaky! I printed out all the information from my previous loans to them and noticed how much I have paid over the legal amount owed!! So I sent them a c&d letter, and let them know I only owe them $44.00--due to all my past extension payments!! They have not responded and I can no longer log-in to their website.
I have to thank this forum and website for helping me through this. There is so much information on this website I wish I had known 1 year ago!