Right now, I'm looking after a pair of small rat type dogs, and the stupid things won't stop barking. I love proper dogs, and I get on well with almost all decent sized one - even the aggressive ones that I am told are difficult. Thankfully, it is only for today, and I'm not going to do it again. I've tried talking to them, and bribing them, but it doesn't seem to shut them up. I just don't understand why people keep the stupid things (small rat-dogs).
I have a dog at home, I get really scared when they don't bark... 
I think you are just not used to their barking yet, or you are a person who doesn't like fuss. if you get really annoyed like the best way you can take is just to sell the dog back.