Unfortunately, we are not able to re-stretch carpet because it is not a service provided by Lowe's. A quick Google search for "carpet stretching services near me" should help you find a local professional to do the work.
When having your carpet re-stretched, be sure all the furniture is removed from the room and the carpet is power stretched very tightly in all four directions. Often, older carpet will start to wrinkle as it ages and the backing begins to break down. If your carpet is older than 10 years, re-stretching will not be a long-term solution.