Bed bugs in rental unit. Landlord won’t pay for extermination.

I’ve been reading here for a few days now and thought your helpful advice may be able to help me. I told my landlord in mid march that I thought I had bed bugs. My landlord send out an exterminator who then determined that I had fleas. The night before they were supposed to come to exterminate, I found a bed bug on my bathroom wall. I took it down to property management and showed it to them. They showed it to the exterminator who then confirmed that it was a bed bug. I asked them who would be responsible for extermination as there was some question as to whether or not they would be checking other units for infestation. I was then told that I could have brought the bed bugs home from the grocery store. This may be true, however, the following Saturday, I learned that my neighbor across the hall has bed bugs, and his infestation is far worse than mine (he mentioned up to 100 bites per night and actually finding the bed bugs living in his mattress). I have flipped over my mattress and looked everywhere. My house is totally prepped for extermination, and I have yet to find their hiding place, and I hope I never do. My neighbor told me that property management agreed to pay for his extermination after several hours of arguing with them. I went down to tell them that I would likewise not be paying, and they then proceeded to tell me that I must have brought them in because they don’t travel across hallways. I find it hard to believe that I can bring them home from the grocery store but that they wouldn’t be able to traverse a hallway. I live in Seattle,Washington. The laws seem to be in my favor, as they cannot prove the infestation came from my unit, especially with a neighboring unit having them. However, I am still being told that I will have to pay for the extermination. 

FYI no fleas were ever found in my unit. Not even by the exterminator they sent out. Property management also acted surprised to learn of my bed bug infestation despite the fact that they already knew of my neighbor’s situation. I’m not sure what my next steps should be. I have called the regional property management company but they refuse to respond. I have also sent my management company a certified email via rpost, which they deleted. Any help is greatly appreciated.