Failure to update address

I have been trying for more than a year to get Link to update my address from SA to New Zealand. They wanted a letter from the Standard Bank that I'm a genuine emigrant and Standard supp**** that (I have a copy). Apparently Link did not receive it (it had to be by surface mail). Link then asked me to send them certain certified documents by surface mail from New Zealand, which I did. Again it seems these were not received. They were not registered because the registration would fall away as soon as they left NZ and I have every confidence that the NZ post office delivered them to the airport. After many emails from me to Link, Mandy Smith said I could email her my documents, so I had them certified and emailed them. Since then nothing has happened. I emailed the documents twice and sent a reminder, but there's no response. I'm now used to efficiency here in NZ and cannot believe Link's service is so bad. My next step will be to escalate this to Old Mutual.