Collections agency upset my last check bounced

Can a collections agency add themselves to your credit report? I've already got the original "charge off" from the creditor, but now I'm dealing with an upset collection agency who was upset my last check bounced. They're the ones who forced me and harrased me into writing post dated checks to begin with, they called my work and when I told them not to they laughed at me and told me that I couldn't tell them not to. Now that balance for the amount of the third check is on my credit report too, is this legal?
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the original charge should be marked as zero balance if it was sold to a collections agency you have verified the debt now that you have paid them monies
the collection agency CANNOT sue you as they are not the original creditorI know they cannot harrass you or call your work over and over and laugh at you I would try to settle the account for much less than the full balance. most collections are bought for pennies on the dollar. I would try to settle for 50% of less not including any fees or interest. demand account validation Explain you will talk to them no longer if they do not properly validate the debt. explain you fill like they are violating your rights and plan to contact your state attorney general if they insist on calling you at work after you have asked them not to