This would be a website with a blog attached to the site for sure. Here is why:
A website is normally for a business and it is easy for them to advertise on the site about how you repair the phone.
You can add your contact, pricing, repair order tracking and mail information to the website.
You can integrate a tracking and repair order on the site.
On the blog site, you can write articles about phone repair to show people you understand what you are doing.
If this is for your business go with a website and have some blog posts on the site that people can read and follow. This is more professional than a blog site for sure and you'll earn a lot more business if you have a professional website and not just a blog site.