On the proviso that you were issued with a Bestätigung über die Antragstellung (https://www.ris.bka.gv.at/Dokumente/Begut/BEGUT_COO_2026_100_2_1798418/COO_2026_100_2_1798439.pdf) which provides proof you have applied for an Article 50 card under the Withdrawal agreement, you are allowed to stay in Austria until all appeals are exhausted. The BMI answered the question re. AMS in at least one of the Embassy outreash events. See the answer to Q6 in the September 2021 Embassy outreach event. https://www.gov.uk/government/news/british-embassy-outreach-events-in-austria. Did the Brexit hotline provide these answers in writing or was it verbal?