no aggressive breeds, what do y'all think?

Quyen • Diagnosed with Unexplained infertiity.
So Jan 16, my husband I & adopted a pit mix. But before we could adopt her, we had to make sure that our property manager ok'd it, so the humane society contacted her, stating this she is a pit mixed & was wondering if her breed is allowed. my apartment manager at the time, said that was fine. We also discussed it & asked her permission before adopting our sweet girl and she was okay with it. Willow is now 14 weeks, & doesn't have a mean bone in her body. She actually came from abusive owners before us so we are happy that it didn't cause her to be scared & agressive, as she loves everybody. But today I came home to a letter saying I violated the lease agreement Bc I have an agressive breed pet & have not paid the pet desposit. The reason I have yet to pay the deposit is Bc our old manager which I have proof, told me I didn't have to pay it until the end of this month. I also went on & told them that the old manager did okay this & I do have paperwork for her stating she is mixed & has all her shots & what not, but they are still trying to tell me she isn't allowed. Apologizing that the old Manager didn't know what she was talking about it, but I feel like that's too bad. They should have been more clear to the old manager instead of bringing it up now, a month after we'e had her. I even went on their website where it states that "SOME agressive breeds are restricted" which I understand if she was aggressive this wouldn't be a problem, but she is technically "mixed" and not one single tenant here has complained to her Bc she isn't mean at all. Our apartment we stay at had to change both regional & property manager, which is why this is happening. I'm really fustrated as I went through this with my old manager & now they're telling me that they need proof of the old manager stating she knew Willow was part mix..I don't have any as we spoke on the phone... is this fair? 
UPDATE: so I called the regional manager myself & told her everything that is happening & she has agreed to let us keep willow! She says as long as we take her to the vet for a temperament test to make sure she isn't agressive, they don't mind.  After the call, they sent out an email to the whole building about the breed policy. And how everyone now needs to pay their pet fee BEFORE bringing any pet to the premises. Apparently our old manager told myself & the other tenants we could pay the pet fee in Feb & they didn't like that. Just glad they are letting us keep her!  
 
This is her & her brother Moose & how they love each other!