Memorandum of Appearance

In a civil case, an advocate purportedly appearing for respondent filed a memo of appearance and asked for time. No vakalatnama was filed by him . Memo of appearance was also not stamped with welfare stamp. My understanding is that memo of appearance is no substitute for vakalatnama and it can be filed only for extending the scope of vakalatnama already filed. Am I correct and whether that advocate can be challenged on this ? Shall be grateful if eminent Experts kindly advise.