Can the collection companies access your cell numbers?

Yep, cell phone numbers as well as home phones are listed on your credit report, which is one of their skiptracing tools.

Most collectors use the method of skip tracing the individuals. Credit reports are checked looking for the addresses used by the people. There are some collectors who get in contact with the utility companies and phone companies and get your cell phone number. Using the last name, many people are contacted until they are able to locate you. If you have used someone as reference, most of the information is tracked from them also. Besides, there are many other ways used by CAs to contact you. Although most of their collection techniques often sound illegal, the best way to tackle the problem is to call them and get the information verified. If they don't have a genuine purpose to contact, your name must be immediately removed from their system. Sending a cease and desist letter also helps if you are sure about them making wrong contact.