From what is aware POTRAZ are not yet regulating the service (registering of bulk SMS providers), however they are concerned about the customers to whom you intend to message. POTRAZ will be interested to know how you got the customers number (as in was it with their consent) and also whether you will provide a means for that user to opt out of receiving your communications.
Further, the Mobile Network Operators (i.e. Econet, Telecel and NetOne are slowly blocking the sending of bulk messages to "their" subscribers because this circumvents the network and "deprives them" of revenue.
For now, I would advise you to tread cautiously in this area and not to make any hasty decision or any large capital outlays.
From previous questions on this platform (http://answers.techzim.co.zw/8741/are-bulk-smses-delivering-to-econet-numbers-in-zimbabwe
) there was suspicion that Econet were blocking the delivery of their international sms gateways and thus prejudicing local businesses of potential revenue. Your best bet in this regard would be to approach Econet and find out what "official" (through local networks) channels can be used to deliver your messages