False creditor information ruined my credit score

[Tim V.]

Spoke with my bank today about financing my next real estate purchase. 

On my credit report was an apartment complex where I broke the lease but paid all early term fees. I have all information saved luckily 

on Feb 22 I sent an email the the debt collector, they stated that if the information checks out they would stop with collection proceedings. On Feb 24 they submitted to my credit report, and each month since. 

Today I called and they said the account was submitted by error from the Apartment complex and closed out on their end but the debt collector cannot remove it from my report. Only the apartment complex can,  the apartment complex will not return my calls. 

Im selling a home now that I hoped to roll the proceeds into a 1031 but everything is in limbo now because my bank may either kill the deal or charge much higher interest rates due to this error and lower than expect credit score. 

I just found all this out today so Im asking for any advice how to handle this quickly considering I have all the proof I need. Its my understanding that disputing the credit agencies can take up to 30 days so I plan to do that asap. Ill email the Apartment complex tomorrow to start a paper trail. 

If my 1031 gets cancelled due to me not being able to attain financing then there must be damages to me financially? Should I start speaking with attorneys?

Sorry for the wordy post. I tried to keep it as simple as possible without leaving out to much info. 

Thanks everyone