Answer: The HiLo can store up to 100 SMS in his flash memory. However, it can also store some SMS in the SIM card. You can choose your preferred memory by using:
< AT+CPMS=“SM”,“SM”,“SM” > to select a storage in the SIM card.
< AT+CPMS=“ME”,“ME”,“ME” > to select a storage in the internal memory of the HiLo.
But you have to keep in mind that each SMS has a CLASS.
This CLASS may force the HiLo to store the incoming SMS in the SIM card, in the HiLo or nowhere.
Please find "Table SMS Storage” in AT document for more details.