Read our article HERE on the differences between Campaign and Direct Dial Numbers. Make sure that you are configuring the correct type of number for your inbound/outbound process.
1. Go to Settings>Phone>Phone Numbers and click on Manually Add Phone Number. 
2. Search for the Area Code you would like to purchase and you will be given a list of all available numbers. Check the "Agree" box and purchase a number.
Note: If no numbers pop up, there are no numbers available for purchase with that area code. Check back later, or try a nearby area code.
3. Follow the template below to properly configure your Direct Dial number. 