A digital recorder is nice and all, but if you plug a recorder directly into an iPhone using a 3.5mm audio cable, you're not going to hear the call. Using the iPhone headphone jack—assuming your iPhone is so old that it even has one—cuts off the speaker. Get the Recap-C, a $99 adapter that plugs into an older iPhone's 3.5mm jack, with output to a headset as well as to a recorder. The secondary recorder—connected via a 3.5mm male-to-male auxiliary audio cable—is up to you. It could even be another iOS device (or Android or PC, but stick with the digital recorder for simplicity).
Apple Visual Voicemail is available for free for all Truphone iPhone customers with a data plan. Truphone does not charge an activation or monthly service fee.

Voicemail access and the initial password should have been set by your carrier or service provider when your device was first activated. But keep in mind that some carriers don’t use passwords when it comes to voicemail. If you don’t know if this service is enabled or you forgot the password, you should check in with them first. If you see the contact list opening, tap on the phone dialer icon located in the bottom-right corner.Once you’re in keypad dialer, touch and hold on number 1 key. Now one of two things can happen. One, if you the service is enabled your phone will dial the voicemail number and prompt you to insert or create a new password. You might also be asked to record the greeting message at this stage. And two, in case your carrier didn’t configure this service when your device was first activated, you’ll be prompted with a message to insert your voicemail number. If the first scenario is the case, follow the instructions provided by your carrier to finish setting up your voicemail. In the event that you’re prompted to insert your voicemail number, tap on Add Number. If you don’t know your voicemail number, call your carrier and ask for it or search online for something like “voicemail number + *YourCarrierName* + *YourCountry*”. Now follow the instructions provided by your service provider to finish setting up your voicemail. Note: If you bought a used phone or you recently changed the service provider, chances are you have the wrong voicemail number set up. In cases like this, open up the App drawer and tap on Phone. From there, tap on More and select Settings. Once you’re in Settings, scroll all the way down to Voicemail settings and tap on the entry. This will open a pop-up in which you can change the voicemail number.
Setting up voicemail accounts on your US Mobile line is quick and simple. It simple, and only takes a few minutes! Follow the steps below to set up Voicemail Setting up voicemail on GSM LTECall 123 to connect to your voicemail.If prompted for a password the first time you access your account, use the last four digits of your phone number.When prompted, create a password which can be any 4 to 7 digit code. (A good password is one that’s easy for you to remember, but hard for others to guess)When prompted, record your greeting and name.Your voicemail is now ready to use.Setting up voicemail on Super LTECall *86 to connect to your voicemail.When prompted, create a password which can be any 4 to 7 digit code. (A good password is one that’s easy for you to remember, but hard for others to guess)When prompted, record your greeting and name.Your voicemail is now ready to use.Setting up Visual Voicemail (Super LTE and GSM LTE both)