I have a 30 lap watch & cud not swicth off the alarm. if it is just beeping, hold the set button, & browse through pressing next untill u reach the chime & beep...press the + or - , to switch it off.
to switch off the alarm, press mode twice ( in my watch) till u get the alarm setting & you should be able to swicth it off.

I think the battery is low voltage,try to change the battery 1

Try pushing the two bottom buttons

I have the same watch. Try pushing together the two buttons on the right. You will see the bell vanishing from the screen upper left side.
Good luck.