gsm module , shows DNS error after several days

So I made an arduino project to send data to database everyday for reporting. The connection that Im using is gsm module. For the first 4-5 days the arduino works fine and the data were sent each day without a problem. However, on day 6 or 7 the arduino shows DNS error and the whole module stops completely and never send data again unless I restart the arduino. I’m suspecting it has something to do with the RAM. I tried changing the gsm module 3 times and this problem still persist. Is there anything that i should be aware of other than the RAM? Thanks.