Problem executing CRM_SERVICE_ORDER_CREATE_IT with system user

Hello,

My problem concerns an RFC function that uses the following functions:
CRM_SERVICE_ORDER_CREATE_IT
CRM_ORDER_MAINTAIN
CRM_SERVICE_ORDER_SAVE_IT.

The RFC is supposed to create a new service order, but it doesn't succeed in doing that.

The problem is that the user type that runs the RFC is a system user. The system does not allow system user to use the 3 standard SAP functions.

I don't want to transform the user to dialog user type because it means I would have to change the password every 2 months and it's a big burden.

Can you give me an applicable solution for the problem?

Regards,

Guy