I'm posting here because I chatted with a person on your Help system and she indicated there is no other way to contact Ting about a feature request.
I switched from AT&T to Ting in July, and it is a HUGE disappointment that Visual Voicemail on iOS is not supported by Ting. I have missed numerous important voicemail messages because VM's are not stored on my device and Ting's coverage is often spotty. I rarely get any alerts that new Voicemails have arrived. Over the weekend, I checked my voicemail and found that I had 19 saved voicemails even though I had not gotten a single alert. Frankly, this is reason enough to move back to AT&T, which would be a huge disappointment.
In a previous forum post from 11 months ago, someone from Ting indicated that they were working with Apple to implement this feature, which is standard with all other carriers for iOS devices. However, the person who I just chatted with in customer service said that there are currently no plans to implement Visual Voicemail for iOS. Please know that you will likely lose at least one customer if this feature is not implemented. I would rather not return to AT&T but I'd also rather not go back 8 years in voicemail technology.