An effective way to prevent segregation of duties issues in an enterprise resource planning (ERP) system is to grant user access using a role-based model. This means that access to systems and applications is based on the role or job function of the user. This helps to enforce appropriate segregation of duties, so that critical tasks are not performed by the same individual, reducing the risk of fraud or other security breaches. A role-based model allows for the efficient and effective management of user access rights, helping to ensure that the system is properly configured and secured.
Reference:
ISACA. (2021). 2021 CISA Review Manual, 27th Edition. ISACA. (Chapter 7, Security Administration)

The best way to prevent fraudulent payments is to implement segregation of duties between the vendor setup and payment processing. Segregation of duties is an important control measure used to mitigate the risks associated with fraud and errors. By separating the processes of vendor setup and payment processing, it ensures that no single individual has control over both activities, and thereby reduces the risk of fraudulent payments. Additionally, other measures such as dual authorization and automated controls can be used to further reduce the risk.