How do I send money from my MoMo account to OPay with ussd

I have a Huawei phone, I have MTN & MoMo App installed. I have MTN airtime, & I would love to be able to send my Mtn airtime into my MoMo wallet. Can you please assist me with...

When I try sending money they tell me sender S account not active

I lost my phone last night and I want to login my momo account to withdraw out my money but momo send a verification code and I can't access the code to login.Please i need help...