No. You don't get to choose which company services or collects debt from you, sorry.
Sallie Mae "originates" private student loans of its own, but they also are the "servicer" of some loans, and act as the "collector" of other loans. The loans that they are collecting from you could be federal loans or private loans, there is no way to tell just by knowing that Sallie Mae is calling you to collect.
But in any event, if they are the servicer or collector of the loan, then they have been assigned that role by the owner of the loan. You cannot change the company that acts as the servicer or collector of your loan, but you may have other options to repay the loan that they are not telling you about, or that they misrepresented to you.
I have had student loan debt collectors lie to my clients and lie to me about the repayment options that my clients have. One client even called the Dept of Education and told them, "hey, your debt collector lied to me," and the Dept of Educaton rep said, "well yes, sorry, but they do that." It has to do with how the collectors are compensated - commissions. It's really a national disgrace, is what it is.
If you have having problems with your student loans, cannot pay them and do not know what to do and live in the Houston, Texas area, contact our law office at 713-772-8037.