i am not sure if this works but since you have no time suggesting this... don't recharge and carry on with your journey. If they disconnect because of no recharge plan then it is fine, leave it like that. You wont be there at home in these 2 months anyway if those guys comes to check the issue or to collect the router/safe custody bill. Now when you are back after 2 months, recharge it with same plan or other if it works.
Also wait for other dimers replies
if your connection is prepaid.. then do nothing.
if postpaid then it's better to raise disconnection request, they will then call 2-3 times for reasons for disconnection, tell them your exact problem, maybe you can pause your connection without paying anything... if they don't agree then tell them to proceed with disconnection.. after that they will send someone to pickup only the router and adapter in 1-2 days (leave the router with neighbour or some frnds )