As a Sprint customer, having online access to text messages sent and received to the phones on your cellular plan would be convenient. Unfortunately, Sprint's privacy policies do not allow an account holder open access to any texts sent or received on your cellular plan without the involvement of law enforcement.
Contact Sprint Customer Service, which will advise you of the number of text messages used on your account. According to Sprint Customer Serivce, the additional details they are allowed to give an account holder of those text messages require a telephone call to Sprint's Corporate Security at (800) 877-7330. Corporate Security will require a notarized letter indicating that you are the account holder on the account in question.
Contacting Local Law Enforcement
According to Sprint Customer Service, you must contact your local law enforcement agency if you wish to acquire the content of the text messages on your account. The local law enforcement procedures must then be adhered to for your area.