After retiring at the age of 50, Zhang (female) receives a monthly pension 1500 yuan. Three years after retirement, in an activity organized by retired workers spontaneously, Zhang and his retired colleagues talked about their retirement life, and inadvertently found that they received less 350 yuan pension every month than their colleagues with the same conditions. Zhang immediately questioned the personnel department of the unit and did not get a reasonable explanation, so he went to the local social security fund management center to inquire. After verification, the center informed Zhang that there was no problem in calculating the pension according to the amount she paid over the years, but reminded Zhang to pay the pension according to the lower limit of the average monthly salary of local employees in the previous year for many years, which affected the pension level. At the same time, at Zhang's request, the center gave her a record of payment over the years. Zhang asked the unit to provide her payroll for the past years, but was rejected. However, Zhang usually has no habit of saving payroll. He rummaged through the cupboard at home and found only a payroll for one month five years ago. Comparing the payroll and payment records, Zhang found that in this month alone, the company underpaid and embezzled 160 yuan by deducting 400 yuan from the payment base of 5,000 yuan, underpaying (actually paying 240 yuan), etc. Zhang couldn't find a reason to find a unit, so she consulted a law firm, and the lawyer asked her to defend her rights through relief channels.