@秀也 渡邊 Welcome to Microsoft Q&A Forum, Thank you for posting your query here!
I understand that you received an email from Microsoft asking you to upgrade Azure. You are currently using the free version and using "speech to text". You are concerned whether you will still be able to use speech to text for free for the next year.
In short, you should be able to use the free tier for Speech service for next year.
Please note that, Microsoft Azure offers a free tier that includes a limited set of services with certain usage quotas. The free tier is intended to provide you with hands-on experience with Azure.
The quotas and limits that apply to the Speech service for free vs Standard sku is explained here.
Also note that if you exceed these limits for your free sku you will receive response from speech service as 429 error.
For the free (F0) pricing tier, see also the monthly allowances at the pricing page.
If you have any follow-up question, please let me know. I would be happy to answer.
Please do not forget to "Accept the answer” and “up-vote” wherever the information provided helps you, this can be beneficial to other community members.