Customer complaining about item purchased 7 months ago

A customer bought a kit off us 7 months ago and has just contacted us to say we sent some wrong components out and he’s only just realised as he hadn’t unpacked the kit till now. We’ve told him that any mistakenly sent items need to be reported within 30 days or we can not send out the correct items. He’s now saying he’s contacted his solicitor and is going to take us to court. Obviously he’s talking rubbish but how should I proceed?