not sure if right for your project, but an idea ive had in the past is that the organizations should have the jobs filled by people from the places they are organizing support for.

too often the work involved in taking it to an organization level is written off by the doners, and / or taken advantage of by the org. but renting a building and hiring people to take calls, perform accounting, etc has real cost that cuts into donations but it is also an area of job creation. Those jobs created, imo, are incredibly important and when they are given to people in the donating country it turns into mostly just economic activity in the doner country run on donations with just whatever amount is leftover going to the actual aid. of which, without any outright corruption, people are always eager to spend that money to make the organization side of things better.. or invest it into the organization under the guise (genuine or not) of scaling the organization such that donating a bit less today leads to more donations tomorrow. and then it becomes like any other business mostly running on debt and the actual donations are like a material cost that is constantly pressured to be cut down to pay back debts

The simple solution is to always have such calls be monitored by another adult.