Hi and Welcome.
Ok...
1)Yes, unfortunately that is possible. What might have happened is that even though you "settled" with the OC, they could have sold the remaining amount due to a CA. It's shady, yes, but unless you have something stating that they will not sell the remaining balance to any 3rd party collectors, you may be out of luck.
What I would do is take a copy of that letter from the OC and mail it (CMRRR) to the CA that is attempting to collect on this. Is the debt out of SOL? What is amount? If it is not a substantial amount (worth suing over), I would even send a FULL C&D along with the letter from the OC. Just depends on how ballsy you want to be.
2)Are these out of SOL? Usually phone and cable fall under the UCC SOL under goods and services which is 4 years.
And no, if you send them a letter I would not really advise that one. They aren't going to take the time answer your demands anyway. Just a short and simple dispute is better, IMHO. They know (by law) what they are
supposed to provide, you don't have to spell it out for them. Plus that
looks like a form letter.
3)That's an odd letter. :confused:
Have you received your results from the CRA on that one? (or any of them for that matter) If not, I would wait and see. Not really sure what they are asking, I mean, duh...you are disputing the debt.
If you have already received your results as verified, then just send the CA a DV letter ignoring the letter they have sent you.
It would be good to know the SOL status on all of these just to make sure you are on the right track, but no, you didn't mess up by sending out the dispute letters to the CRAs. Sometimes doing that just makes the CAs crawl out of the woodwork.
One thing I would definitely suggest is opting out and update/deleting all personal info before you do any more disputing with the CRAs.
HTH