Overdue backpay from DWP

Hi, what happened was i was on incapacity benefit from 2007 to2014, i was then canged to esa con based, iwas also on pip enhanced rate for care, from 2014 to oct 2018,when my pip was reviewed in feb 2018,and i had my f2f, i was sent out lettets to say i was now on income based esa, so my money had now gone up from 213 per fortnight to 360,due to my pip etc, i wd be getting sdp, which i was really pleased abt, prior to this happening i had wrote to dwpin November time asking  if my esa, group was correct i thought i shd be in income  group due to my personal circumstances,
So when i got all the information in feb, i rang explaining i had wrote to them last yr, an was told yes ur case as been with decision maker sinse jan 2nd 2018,re sdp payment, from when u first went on to esa ftom incapacity  anyway, i was called bk asked questions, etc etc, an last week was told yes u r entitled to back pay, the decision maker has agreed, but will bedone clerically, u will get itin bank next week, which wd b this week, so i rang today to see if things were progressing, to b told, nothing on system, abt any payment been made to me, i just dont know wat to do, she said i will b called bk within 48 hrs,iam really  not getting any where with it, thanks for reading my post