In order to get help and receive a particular service on the platform, you will have to pay the price that the other user you want to connect to has set on the platform. When you try to reach someone over the phone, you will pay for the time per minute.
Everytime you find a user you would like to connect with in the plaftorm, you will have a chance to review the price that this particular person charge for their time before you decide to proceed with it.
For example, if a particular user charges $2 per minute of her time, you will find the information on your screen before you decide to accept the connection between yourselves. The price that you will pay for that particular conversation will depend on that price (in this example $2 per minute) and the time you end spending on the phone with that particular person. If you spent 5 full minutes with that user who charges $2 per minutes, your credit card will then get charged $10.00 at the end of the conversation ($2 x 5 minutes).
For messages or other features of the platform you use to contact a particular user, a similar mechanism will take place. Pricing in that case will depend of what you are using. You can find more information for chats and messages here.