The company went to the Social Security Bureau with a letter of introduction.

Of the five insurances, only endowment insurance can be transferred. As long as your social security is suspended, you can bring your ID card to the local social security window, and the window staff will print out the details of the old-age insurance paid locally and stamp it for you. This certificate has no time limit. After taking this certificate to the corresponding social security window in a certain place, your social security pension will be transferred to a certain place.

Further reading: How to buy insurance, which is good, and teach you how to avoid these "pits" of insurance.