Battery draining extremely quickly

Have you cheked the battery health?

See this excerpt from the "Your battery's maximum capacity" section of the support article: iPhone Battery and Performance - Apple Support

"A normal battery is designed to retain up to 80% of its original capacity at 500 complete charge cycles when operating under normal conditions. The one-year warranty includes service coverage for a defective battery. If it is out of warranty, Apple offers battery service for a charge." In other words, if maximum capacity is below 80%, the battery is below normal performance. You can still use a device with a lower health percentage than 80% but for optimal usage you may wish to consider having it changed when it reaches 80%.

Batteries are consumables and 1-2% loss per month is perfectly normal. According to iPhone Battery and Performance - Apple Support , Apple apparently only considers it unusual (and warrant-able) if a battery drops below 80% maximum capacity in less than a year after you receive it. Ergo, some storage loss as you use it is expected and acceptable. Incidentally, that possible 20% drop over the first 12 months equates to 1-2% drop per month being within the range of what Apple finds acceptable.

Go to this web site for information about how to request battery service for your iPhone: iPhone Battery Repair & Replacement - Apple Support

For cost and availability, enter your model information in the "Get an estimate" box at the bottom. (I will let you do this since the answer will depend upon the country where you are located.)

For instructions on how to get your iPhone, iPad, or iPod touch ready for service click here --> Get your iPhone, iPad, or iPod touch ready for service - Apple Support

Go to Settings/Battery and see which app or apps are using the most energy. And note that if you have a weak or no cellular signal the phone will use a lot of energy just to maintain or restore the cellular network connection. This might happen if your golf course is far from the nearest cellular tower.

Try restarting the device.

Certain apps or services may be running in the backgroup. Try quitting certain ones or restrict them to only using related features when the app is actually in use. Social media apps may be constantly connecting to check for updates.