Ringtones Problems. It didn't ring whatever I set individual

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It didn't ring whatever I set individual ringtones. Sometimes it didn't ring whatever I set individual ringtones, but it rings default ringtones.. I've read same solutions to solve the problems here. Some said it might be related to # in sim card, you have to use sim manager to set the same #.. but I found that I don't have # that I get problems in Sim card anyway. Now I delete all # in sim card.. Anyone can help think about this problems? Thankz a lot.