Kind of an 'as featured in' type of graphic? I don't think there would be a problem unless you use there own logo in the graphic which would be protected under copywrite, I guess. I'd ring the department you spoke to regarding the piece to check on that. But they can't really stop you from saying you've been featured in their publication!
Personnally I'd ring them and say you were going to do it - using their logo/brand will give it more credibility - plus if you get on the right side of them, they might choose to feature you more often in future.
__________________ Thinking about sending Christmas Cards?
Well, why not send as many Christmas ecards as you like for only £5.99, save a fortune, put your company name on the message and be green at the same time