VOIP provider needed to link global offices

Hi,

My company is looking to use VOIP for our phone calls, hopefully within 6 offices around the country. The UK seems easy (3 offices are there), there are lots of suppliers that can help us out. We have offices in South Korea, Japan and Malaysia though which is a little trickier. We could connect them all back to a VOIP provider in the UK over the public Internet, but the latency and packet loss is really quite high and I'm worried about the reliability.

Are there providers out there that would cover those 3 countries and provide a local SIP gateway in each? I'm hoping to find a massive company that owns big parts of the Internet backbone and can provide a link back to the UK with really few hops.

Just to make things worse, we want to keep our local phone numbers in those countries, so it would be good if the supplier could port them over to the service.

My alternative plan is to find a company in Japan, as the link to Malaysia and South Korea seems alright from there. The issue with the porting of the numbers still remains though, that supplier would need to support the porting of Malaysian and South Korean phone numbers ideally.

Does anyone know of anyone that could do something a bit like this? Any help is appreciated!

Thanks