Isn't O2 in NL now Telfort?
So far with my limited skills in Dutch (and mostly a free online translator

, I've found KPN to roam in Canada in prepaid, Orange does not seem to roam on prepaid and can't get a clear answer for either Voda NL or T-Mobile NL (even Telfort).
As for English customer service, only Voda NL seems to have it.