Basics modeling questions at BPMN


i am new at the bpmn modelling and have some questions.

I want to draw a model of a process. The process beginns when a customer contacts the company. He can call the company, write an email or visit it. How can this decision be implemeted in bpmn (with an extra pool for the customer and without the extra pool )

At another part of the process should be a decision: if the customer pays the bill, then action 1; if not action 2. How can this process be implemented in a bpmn model, when the customer is a seperate pool?

Thanks in advance