My group has bought unit trusts with the company but we're difficulties to redeem them due to a supposedly ref

My group has bought unit trusts with the company but we're difficulties to redeem them due to a supposedly ref. number they gave some 30 yrs ago. Due to changing of members serving on our executives panel, we can't track back the reference number. However Sanlam acknowledges the business we are engaged with them but irrespective of the information requested from us of which we comp**** to, it's been almost three years without any progress.