Silent treatment from courier

I ordered & paid for courier, received an sms on the 3rd of May from Buffalo stating I need to pay 150 for a second delivery of my parcel as it was returned to the depot. There was no communication on when the 1st delivery was happening or when it happened which baffled me as I am home all the time. Sent an email, tried calling & msg via WhatsApp(which they say has a quick response) but no answer. I now want to collecty parcel but as they are not responding don't know what to do as dealing with them is frustrating. Will never buy online ever again if this is the type of courier service used.