Sainsbury’s bank corrupted me

Last October i joined Sainsbury’s and since then there was a problem with my tax code and HRMC was taking more than 50% from my pay checks and my managers told me they will fix it, so to live i had to take a credit card loan, and fast forward to November and December they still didn’t fix my tax code and i wasn’t getting paid basically noting and i still had to take credit card loans and help from my struggling mom, now today i was hoping to get paid £2.5K because i had worked over 125 hours, plus i had holiday and i was hoping to get my tax back but guess what they still didn’t fix my tax code and i got paid less than £1K, and i was supposed to pay back £1.2K by the end of next week and i remember i promised my mom i would pay back my loans and take her to shopping, but how do i tell her Sainsbury’s bank corrupted me, and what fault do i have? First they didn’t keep me and they kept the uni girls for obvious reasons and now they are making me bank corrupt, i honestly regret joining this company