Sars complain

Early October 2020 i submitted my tax returns at Rissik Street Johannesburg, they sent me back to get onother RIP5 from Alexander Forbes since i resigned from my previous company, i got it went back to Sars everything was fine i got an sms confirmation of my submission i was owing Sars R181. 00 was prepared to pay it i received an email telling me to log in the Sars e filling, i did to my surprised this morning i recieved new statement from Sars telling me that i owe R25 thousand rand i called Sars requesting to get an appointment to find out what's going on their consultants confirmed that i owe this huge amount that i don't even know where they get it I'm requesting to go to the branch apparently i can't go in I'm really frustrated because i can't sit with this huge amount i need assistance apparently was assessed twice if how is that possible i don't know how can they access me for 2021while the year haven't started and where do they get that amount, been on the working field for 9 years now I've been submitting since i never even skipped a year i don't do overtime I'm only working at my current company i need clarification please they are ruining my life