Dual Sim (Non worthy in iOS)

It’s very difficult and complicated procedure to use dual sim function in iOS. Please make it simple and easy dialling or texting by giving both sim option before dial or text.

please help me in solving this issue:

I have conversation in sms which I started in using Primary line.. Now I have to use my secondary line for texting which seems to be impossible in iOS unless and until you delete the whole conversation and then use secondary line as texting...

please solve this issue.