when did the bookies start changing the ods on your betslip

man im using betfred at moment and i only do multis with bookies £2 multis and still banned of 90% but freds kindly letting me play and unlike most ive been alllowed to win a bet and stay .
but wtf is going on with the odds changing while im putting them on the slip.theres no way every time say like now midday 4 of  5 horses just went down now ,its happening every single time so it must be on purpose.big r was 11/4 and i deposit click the fuukin box sayin keep selections and like always it deletes them and by the time i get em back hes 2/1 lol .and the other 4 shorties ha all gon down a fraction.
ive read about usa bookies doing it but i always used 365 for 25 y with no problem but since they ban me just problems but ive never noticed any changing the odds like fred.

sort it out fred ffs .i use paddy til i got into it with live chat and they abused the affordability check bs and hacked fuuk out of like always