If you have entered your organization's RingCentral number to Login instead of your direct RC number, then you will face this issue.

Any outgoing call is first placed to RingCentral and then the destination number. When you enter your organization's number, the call is made to this number in round robin or according to the configurations set for any incoming call. As a result, other sales reps receive calls on their softphones.
To avoid this, make sure you log in using your direct RingCentral number instead of the toll-free organization's number.