DVLA is experiencing a lot of delays at the moment due to coronavirus. They're no longer taking paper applications, it's online-only currently for renewals. And the phone lines are only being used to help key workers at the moment. I'd recommend continuing to try contacting them about getting your passport back, though.

We've reached out to the DVLA to get some answers about the delays with renewals, but they've yet to respond. Unfortunately, it'll just be a case of waiting until/if they announce something. Unless you're a key worker, in which case you should be prioritised.