My car alarm goes Off various times of day/ NIGHT! electronic car key works 50%

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At 3 AM the first time last week the alarm went off - went out, unlocked the car and locked it again, checked all 4 doors and went back to bed - 15 min. later again! two times more I ended unplugging the battery.... peace at last. Nothing during the day and then NIGHT came again. And again alarm goes off. Unplugged battery went to bed. Next day appointment with service at Hyundai and in the middle of the day now, Alarm went off. Now it does it throughout the 24 hrs at will!!!! The key remote key works 450% of the time. We had told this to Hyundai over three months ago and they claimed that was fixed... it is not. After service and the oil thing recall, the advisor claimed that I needed to spend $150 o sorry $149 dollars to check for the problem which he thought was a comun one where the lock goes half way enough to full the system but not closed all the way thus, creating the alarm to go off! Now he claims even though they DID NOT check the doors and I did not pay for the work NOT done,,,,, That for sure is the problem he had explained to me and the part will be almost $500 dollars. He does not know what the problem is but is ready to charge me $500 to do what? I am looking for a professional and ethic certified mechanic in the area of Petaluma California !!