How do I text secretly on moms phone?

So today i was trying to talk with my Uncle but since i do not have a phone and my mom has his phone number well i decided to use my moms phone with the excuse of finding a word in an online dictionary , so when mom was away i texted my uncle and then deleted the messages. and now my mom got mad at me asking me if someone had called or texted. I don't know whats wrong with this if i just want to talk to my uncle and i did not think my mom would get mad at me.

How do I text secretly on moms phone?
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