Help! Relocating Finanzamt (Berlin)

Hello

I've recently moved to Berlin from Dresden. I will be renting a room for a month from Monday until I find somewhere more permanent. I will obviously register my temporary address, but my main question is regarding the Finanzamt.

I already have a tax number from the time I worked in Dresden and I told them when I left that I would be moving to Berlin. Should I call Dresden first to say I am here or simply go to my local Finanzamt here in Berlin to explain my situation? Is it likely I will get a new tax number?

Please help! Has anybody been through this experience before and know what to do?

Thanks in advance,
Victoria.