esa formal complaint postal address

hi
my self employed group accommodation owner husband applied for new style esa after covid type symptoms at beginning april.he sent application off with the downloaded self isolation form.
since then despite 3 phone calls totalling 240 minutes and dwp admitting that the form has been on system since 20 th april but has been ‘missed’ we are no further forward.they openly said that these claims are dealt with and paid within 9 working days , it is now 12 weeks.two promises for a manager to phone back the next day have been empty.the long calls have made me feel ill as im registered disabled myself and my husband is recovering from prostate cancer treatment(as well as suffering major financial losses from no income from guests during pandemic)
i cant find an address to complain to anywhere, we have no paperwork sent to us as we still havnt had the claim processed.on the last phone call i said i want it putting down as a complaint but im almost certain she didnt as when i asked for the ref number she said its always the nat ins number.yet dwp insist do complsin in first instance by phone
i cant bear the thought of yet another call getting nowhere as the last one was 2 hrs 9 mins for nothing.
is there an address i can write to? we are in north east uk
thank you in advance
kindest regards
suzanne

hi gordon
thank you for replying.i did read the how to complain form previously but theres no postal address for esa complaints.i have found an email address on google and have said that i will be contacting our local mp if this doesnt get sorted.
again thank you for the advice
kindest regards
suzanne