1) An additional telephone call within 7 days is not separately billable and considered part of the original service. Additionally, the 2nd phone call is being initiated by the provider, not the patient. That alone makes it not qualify for 99441-99443.
Telephone services are non-face-to-face evaluation and management (E/M) services provided to a patient using the telephone by a physician or other qualified health care professional, who may report evaluation and management services. These codes are used to report episodes of patient care
initiated by an established patient or guardian of an established patient. If the telephone service ends with a decision to see the patient within 24 hours or next available urgent visit appointment, the code is not reported; rather the encounter is considered part of the preservice work of the subsequent E/M service, procedure, and visit. Likewise,
if the telephone call refers to an E/M service performed and reported by that individual within the previous seven days (either requested or unsolicited patient follow-up) or within the postoperative period of the previously completed procedure, then the service(s) is considered part of that previous E/M service or procedure.
2) The visit should be billed as how the visit actually took place, not how it was scheduled. If the provider had 12 minutes of video/audio, then lost connection and completed the visit with 2 minutes of audio only, I would feel comfortable billing that as video/audio 99201-99215. If the video never connected, then that is not a video visit. CMS has issued FAQs.
https://www.cms.gov/files/document/03092020-covid-19-faqs-508.pdf Specifically section P, #26 (page 75 on the 12/02/2020 version):
26. Question: If the video connection is disconnected during an audio-video Medicare telehealth visit due to technological issues, can the visit still be billed as Medicare telehealth? Answer: Practitioners should report the code that best describes the service. If the service was furnished primarily through an audio-only connection, practitioners should consider whether the telephone evaluation and management or assessment and management codes best describe the service, or whether the service is best described by one of the behavioral health and education codes for which we have waived the video requirement during the PHE for the COVID-19 pandemic. If the service was furnished primarily using audio-video technology, then the practitioner should bill the appropriate code from the Medicare telehealth list that describes the service. Note that CPT codes 99441–99443, which describe audio-only telephone E/M phone visits with practitioners who can independently bill for E/M services, have been added to the Medicare telehealth list for the purposes of the PHE for the COVID-19 pandemic, and payment rates for these codes are set to be the same as the analogous in-person E/M visits. New: 5/27/2020
Remember that's a CMS guideline, and private carriers are free to set their own rules (but many do follow CMS).