Lost parcel and a battle to pay out claim

The Courier Guy is generally good but they delivered a parcel to the wrong address, the driver "could not remember where" and since then we have had a 2 month battle to have them pay for the lost goods. We have to chase them up every couple of days, they will not contact you in this scenario. The support team knows nothing and tells you to follow up per email and no one replies to emails. We have had our branch manager try to follow up and we are now almost 2 months later. They sent a mail saying they are paying the claim in 10-14 days but did not.