China Mobile sent a short message saying that it is no problem to upgrade the communication network without changing the card.

Yes, it does not affect the use. Let me tell you this, because there are card replacement indicators everywhere, and the number of cards pressed by the head office must be completed by branches, users have various reasons to replace the new generation of USIM cards. After replacing this card, the capacity is larger than the original chip, and it can support the signal of 2 3 4G standard. So, there is no harm. The key is that card replacement is free at present. If you change your 4G mobile phone in the future, you may be charged. PS If you don't want to go to the business hall, you can log in to the online business hall of China Mobile to see if you have the right to change the number for free, and then send it to you by courier. I hope I can help you.