well, I would actually fight that, to be honest. going to be hard now because you paid it, but you do have a bill from them stating "final bill", and you have proof that you paid that amount. From that point, it's going to be up to them to prove exactly why you were charged more money after the fact.
But like I said, youre going to have a harder time fighting this, I think, because they already got your money. When you sent the debt validation request to the CA in november, did you send it by certified mail? If so, and if you still have the green signature card from that letter, then you have sufficient evidence to proceed with an
FDCPA violation case against them. you see, once you send them a DV letter within that first 30 days, they are not allowed to conduct any further collection activity at all until they provide you with the validation. Once they got your letter, they ignored it, and then sent you a payment demand letter in December....that's a direct violation of the FDCPA.
here is another thing--if this were me, I would be comparing the dates on your credit report for when they reported this to your report, to the date they signed for your DV letter. if they reported this or updated it as valid at any time AFTER they got your letter, you will also have them on that violation of the FDCPA. that is also considered collection activity and as such is prohibited until they respond to your DV request.
now, i would also be contacting verizon ASAP, and I would explain to them that you want every last detail on that $107 they sent you to collections over. it seems to me that they should still own this account, since we are only talking about a few months time. Something else strikes me as very odd here....you said that in November, verizon still owned the debt, because the CA's letter stated that they were hired by Verizon to collect the debt. So, it seems VERY strange to me that you would have had THREE collection agencies reporting this same debt on your credit reports between November and january. that simply does not seem right at all.
for this reason also, you need to contact Verizon ASAP and inform them that you paid _____ collection agency, and verify that the money you paid did in fact go to Verizon. You may have been defrauded by that debt collector, since in two months time you had three CAs reporting the debt on your credit file. Debts do get sold, but in November Verizon still owned it, and I dont think Verizon would have sold the account that quickly.
----contact Verizon, inform them that you paid ___ debt collector and verify that they got that payment from them.
----at the same time, verify with Verizon why they were charging you this extra money, tell them that you have the final bill they sent which does not show this amount, and tell them that you want to know exactly what you were charged for.
----if you find out that this was a bogus charge, inform them that you want your payment refunded immediately.
----send a DV letter to each and every debt collector on your credit report that put this debt on there. be sure to check all three reports. make sure to send the DV letters certified mail, return receipt requested.
Once you get the signature cards back proving that they got your letters, I would wait a week or two, and then I would dispute every entry on your credit reports that is for this account, no matter what creditor put it on there(except for the original verizon one as long as it is accurate). if any of the CA's verify the debt as accurate, then you will have grounds to file suit against them for violating the FDCPA.