Not receiving monthly invoices

I have been calling Supersonic every month the duration since the onset of lockdown, to obtain my invoices, required to claim for working from home. I am still not receiving my monthly invoices, and calls to resolve is logged every month when I phone. After I sent a complaint to accounts, they responded weeks later advising they do sent it to me monthly, must go to spam, which it doesn't. I have tried numerous times to get a name of a manager, and get told they not allowed to give a name. Asked numerous times for a manager to call me, still no phone call. So still every month I have to call on and hold on for ages as their lines are busy. Honestly, would I really waste my own time calling if I receive my invoices!!?? Disgusting service!!!