Failed lock band ec200a

please help
i have buy hsairpo cpe200 who use openwrt and module quectel ec200a. but i can’t lock band, if i lock band with AT command its will restore to defaut band 8, anyone can help me?
i use “AT+QCFG=“band”,0,4”

Dear, you can try to use this format to see if you can lock the frequency, the first 0 means no no change, so the lock network failed.