I haven't done 12th instead I did Diploma in mechanical engineering and then BE. Can I appear CAT and expect a call from any IIM?

Candidates can check below the minimum percentile/eligibility based on CAT-2025 score: 

SECAB Institute MBA admissions are entrance-based and the institute does not give direct admissions. Students have to appear for the selection rounds regardless even if they have CAT score. However, such students may be eligible for state-level scholarships in some cases. To know more, students can

CAT is widely accepted across most the top-tier private MBA colleges in India besides all the top IIMs, but the scores alone are not enough, especially in institutes like Management Development Institute, SPJIMR, MICA, etc. There are interview rounds and candidate profile selections to go

To get a seat at Bennett University for the MBA/PGDM programme, students have to first attempt the CAT entrance examination, attain the qualifying percentile, and then proceed to the 2nd round of admissions, which may involve GD (Group Discussion) and PI (Personal Interview). 

Based on old data,

Yes, students can get admission in Netaji Subhas University MBA without CAT. The university also accepts scores of other national-level management exams, such as MAT/ XAT, etc. Hence, CAT is not mandatory for NSU MBA admission.