Old mutual is robbing people

My mother in law invested money with old mutual in 1993 and the investment should mature now. Old Mutual is coming up with invalid reasons for not paying out the investment me in full. The contract she signed even stipulates that the matured amount is a guaranteed amount and still Old mutual is refusing to pay the full amount without a valid reason. We are not happy with old mutual and are urging people to never invest with them. If no urgent reaction is taken we will be taking this matter further as the old mutual complaints department is useless.