* Termination fees to fall by 40 pct to 0.15 riyals/min * High fees have benefitted larger operators * Shares in Zain Saudi rise 2.5 pct * STC and Mobily's shares drop 3.3 and 2.2 pct respectively By Matt Smith DUBAI, Feb 23 (Reuters) - Saudi Arabia's telecommunications regulator has slashed call termination fees by 40 percent, a move which is seen as mostly benefiting Zain Saudi, the smallest of the kingdom's three mobile network operators. Termination fees are those charged where a call originating on one network terminates on a**ther network, with the caller network charged by the operator of the network on which the call is received. The Communications and Information Tech**logy Commission, has cut these fees to 0.15 riyals per minute from 0.25 riyals, it said in a statement issued on its website. High termination fees benefit the larger network operators, which have a bigger market share and fewer calls going "off-net" to other providers.