Better advice than using 2 cellphones as a mobile wallet and making transactions.
Instead of buying a extra phone you can buy a hardware wallet and store the seed by writing down on a paper. Hardware wallets are far more better than mobile wallet.
Hardware wallet will certainly be safer compared to mobile wallet, because the hardware wallet has better security and can also be synchronized with your cellphone or computer, depending on the features provided by the hardware wallet used.
The use of a mobile wallet has many risks if you are not aware of its use, one of which is malware that will attack the security of your cellphone. To overcome this, periodic scanning should be done to ensure there are no viruses or malicious applications installed on your cell phone.
But still the use of hardware wallet is better and safer compared to using 2 cellphones as the method you use.