The rules of civil procedure mandate that a party give notice if someone other than a party, counsel, spouse, deposition officer, or spouse of a party is going to attend. Burrhus v. M&S Supply Inc. 933 S.W.2d 635 (Tex. App.-San Antonio 1996, no writ). Assuming there was a violation, neither Rule 200(2)(a) nor Rule 215 specify a sanction or a range of sanctions available for a violation of the notice requirement. However, the overarching principle governing sanctions is that "a permissible sanction should ... be no more severe than required to satisfy legitimate purposes." Chrysler Corp. v. Blackmon, 841 S.W.2d 844, 849 (Tex. 1992). These legitimate purposes "are threefold: (1) to secure compliance with discovery rules; (2) to deter other litigants from similar misconduct; (3) to punish violators." Id. Sanctions that by their severity, prevent a decision on the merits of a case cannot be justified absent a party's flagrant bad faith or counsel's callous disregard for the responsibilities of discovery under the rules. Id. Given these general rules, an appropriate sanction for a violation of Rule 200(2)(a)'s notice requirement can vary and may include excluding the testimony of the non-exempted and unnoticed witness in extreme cases evidencing bad faith or callous disregard. Burrhus v. M&S Supply, Inc., 933 S.W.2d 635, 642 (Tex.App.-San Antonio 1996, no writ). However, a court is not required to exclude the testimony as a sanction for the alleged violation of Rule 200(2)(a).