Can the social security of cities and counties be merged, with the focus on that?

City and county social security cannot be merged. If a person participates in two social insurances, he/she must choose one and give up the other. He/she used to participate in rural social insurance and now lives in the city. If he/she wants to change rural social insurance into urban social insurance, he/she must contact the insurance company and ask them to change rural social insurance into urban social insurance, and he/she must make up the difference between them.