International Incoming Parcel

I have a international parcel coming from the USA tracking number LK18.....61US(Full tracking number available upon request). The parcel is a week over due for delivery and I have contacted the sender of the parcel who told me I should check with SA customs. I have done so and can't get through to customs in Cape Town or in Johannesburg. I need to now submit a claim in whether the parcel is lost or not but the sender insists I cannot do so because he strongly believes the parcel is stuck at customs somehow. Where does that leave me as the receiver. I really don't know what to do now.