Not an option really....just a bearable work-around.
There are some international 'fixed-phone' destinations (US, UK, China, India) that are charged at Kes 3.00 per minute.
Maybe you can explore if some of those are listed on WebEx.
My reasoning is :
Assuming an 8-hour call each day, that translates to 8*60*3 = 1,440/= which in my view is fair enough for such use, which I presume makes business sense.
You may have to do quite some amount of work trying to hack the Destination/Local_Provider permutations though :-)