Elite mobile/Take-alot voucher issues/delays with upgrade

Upgraded in February but never received my take-alot voucher, have been battling 4 months to get a voucher from them. There is always someone sick or maternity leave and the matter is not resolved. No structure in the company between employees where they pass on the work if they cannot complete it, they just leave . AND THEN THE CUSTOMER NEEDS TO CALL THEM TO REMIND THEM TO DO THEIR JO