I have a gorgeous pekenese cross with a japenses chin. He's nearly 6 months old. He's easily trainable and a fantastic dog but occasionaly he doesn't usually listen when I call him. Any Ideas?

Crisp packet in your pocket, works wonders!

At 6 months a pup reaches adolescence and are very much like human ones in that they will test boundaries, want to be come more independent etc.  This is the time for more training, consistency and a god Sense of Humour :D

You got that right :p A longline is a good investment too, as a pre-emptive strike against the joys of selective deafness.  :D

It happens to every pup! :-D

The plus side that I always think of, is that your dog is obviously happy and confident and relaxed enough to want to explore and not need to stick to you like glue, which in itself shows you have so far done a great job with him.

Just continue with the training as already said, it will all pay off in the end, he needs to just get through the adolescent stage when all pups rebel, some just a little, others much more for those that just want to listen to their own minds and not their owners commands as suggested the long line is thee best option.