iPhone battery drain (restore, new battery not solving the problem) possible solution

I have an old iPhone 4 16Gb. I use this phone only to take and make phone calls, cellullar data and wifi/bluetooth always disabled. The battery usually used to last for at least four days without a full recharge. One day suddently the battery started to last less than 8h. I did the normal procedure on those cases: reset the iPhone (last version of iOS 7) and setting as new phone. No effect, the battery lasted the same. I did it again with the same result. Then I remembered that I have never changed the battery of the phone. This phone was used every day for the next 2 years after release, sometimes charged twice a day. Since then has been used every day also but not so intensively. Sure the battery has reduced its capacity below 80%. I changed the battery with a brand new one from iFixit. I noticed some improvement, then the battery lasted for 12 hours (but much less than 3-4 days before). I reinstalled iOS again, no result. Then I swapped to another phone, android this time. At that time I become aware that the SIM was not recognized by the android phone. The iPhone recognized the sim without problems. Here's the solution:

I went to the local store from my carrier to get a new SIM card. Then I insert the sim into the iPhone and problem solved. Now the battery lasts for more than one week. There was a problem with the SIM card that caused the battery to drain (and the iPhone was not hot). So if you try everything to solve your battery drain problem and nothing works, maybe it's worth changing the SIM for a new one. Hope that helps someone, I've searched the internet and haven't found this solution anywhere.