Lost parcel and poor service

I posted my parcel on the 15th of March it arrived in South Africa on the 22nd after contacting Martha which she deals with complaints for international business, she said they have my parcel n it’s with customs cause there is no invoice attached n that we should email the invoice and advised that I should send a person to customs to submit the invoice and collect the parcel. After that conversation I sent my friend to go submit invoice and collect the parcel. When she gets there, they say the parcel is missing and should give them a week to find t , weeks have passed and Martha advised thatif the parcel is not found within a week we should fill in a form to form a complaint, we sent an email to her asking how far is the process she is not replying or answering her phone .