Hello, I am actually trying to do that at the moment while I make my complaint.
I've not had issues with Royal Mail personally, but I understand how frustrating it can be trying to deal with the complaints department of any service provider. They just don't seem to make any effort to solve the problems, even when reported to them over and over again.
The only thing I can suggest is to try and reduce your reliance on Royal Mail. Many organisations will let you opt for paperless statements and correspondence, rather than having them sent out by post. They can usually be sent to you by email or accessed by logging into your account online. The added benefit is that it's better for the environment too.