Yesterday my A52s phone alerted me I had run out of mobile data. I was surprised as I should have had plenty. I also received a text from SIM 2's network provider that I had run out of credit. Again a surprise. On checking the SIM card manager, I noticed that the default SIM for calls and data had changed to SIM 2 from SIM 1. I didn't do that. How did that happen? I contacted Samsung UK support and they said could happen if there was a poor signal for SIM 1. I asked how do I prevent that from happening and they didn't know of a way and contact developers and they suggested I post here.