Toes

Morning all

 Just got a pair of new shoes. My old ones gave me a black toe (second toe), and were worn out anyhow. The running shop (a reputable one) said my old ones were too small, despite being 1.5 sizes bigger than my shoe size and fitted by (another) reputable running shop. 

I now have a pair that are 2 sizes bigger than my shoe size (same brand) and the second toe on my other foot is starting to go black, and the second and third toes on the original problem foot go numb when I run (I remember this happened with my last shoes at the beginning). 

 Are they too big? The man in the shop scoffed when I said that the black toe might be because my shoes were too big. They were expensive and they put me on the treadmill and everything, but surely I shouldn't have to put up with 3 black toes? Or should I? 

thanks

Linds