RigidBody rotating while walling

I created a code so the player can walk forward and left but when i walk forward the object is rotating in that direction but i do not want the object to rotate can someone help me with this?

code:

using UnityEngine;
using System.Collections;

public class WalkScript : MonoBehaviour {

	public bool falling = false;
	public Rigidbody body;

	void Update () {
		if(falling) {
			body.useGravity = true;
			body.isKinematic = false;
		}
		if(Input.GetKey(KeyCode.W)) {
			body.velocity = new Vector3(0, 0, 1);
		} else if(Input.GetKey(KeyCode.A)) { 
			body.velocity = new Vector3(-10, 0, 0);
		} else if (Input.GetKey(KeyCode.Space) && falling == false) {
			body.velocity = new Vector3(0, 10, 0);
			falling = true;
		}

	}
	void OnCollisionStay() {
		falling = false;
	}
}

I think freezing the x rotation in the rigidbody could help