Heating goes off automatically

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Hello,

I observed in the last 3 days the heating it's turning off sporadically even If I did not set it so. Seems it follows the smart schedule which I am not able to delete it. I just wanna set it manually and turn off it manually as well. I tried to delete the block from smart schedule but it goes to 18 degree but it's not deleting, what can I do? thanks in advance!