Notes - the postleitzahl are equivalent to zip codes. For phone and fax purposes - the country code for Germany is 49. Not all phone numbers are the same length. Don't worry about it. I was not able to locate phone numbers for all stores.
Few stores carry more than one or two brands of yarn.
So it is worth visiting more than one store, even in the same town. Brands of yarn are not evenly found across Germany. Regia sock yarn is all over. Lana Grossa is common across the country. GGH, On-line, are more likely found in the north.