Cockroach infestation in new rental apartment, what to do?

I recently became a tenant in my new apartment with a housing association. When I started renovating, I noticed that there was a mine problem and then I was shocked: it was cockroaches. The exterminator was here today and took care of it. But it can take up to 3 months for the cockroaches to go and the exterminator said that they can keep coming back, etc. He said I can move in now, but I have a phobia of vermin and would really hate sleeping next to cockroaches. Now my question is what I should do and can I demand a new apartment from the housing association since they provided me with an apartment to rent which has a major cockroach problem?