Why did 12306 send a text message to adjust my seat, and then I logged in to check or adjust my previous seat? Do you need to call customer service?

No, just press the seat on the text message.

When passengers cannot take the bus according to the date, train number, seat and berth recorded on the ticket due to railway responsibility, the station and bus will be rearranged appropriately. If the rescheduled train, seat and berth are higher than the original ticket level, the excess fare will not be replenished; If the ticket is lower than the original ticket, the bus station or station will refund the fare difference, and no refund fee will be charged.

Change of visa:

Visa change refers to the visa procedures that passengers need to go through when they change their boarding date, train number and seat (sleeper). The railway department reminds passengers that the change is based on the railway transportation capacity (that is, tickets can be sold), only the boarding date, number of trains and number of seats (shops) are changed, and the departure station and arrival station (except the same city station) are not changed.