By Paul Carsten BEIJING (Reuters) – Microsoft Corp. has made it harder to monitor calls and chats over its Skype phone service in China, a freedom of expression advocacy group said, as the Chinese government steps up censorship of the Internet. Skype said on Monday it had ended an eight-year joint-venture with Hong Kong-based TOM Group – 51 percent owned by Hong Kong billionaire Li Ka-Shing – and found a new partner in China. After careful analysis of the new Skype, we believe that Microsoft have lifted all censorship restrictions on their China product, the advocacy group, GreatFire, said on Wednesday.