Hi sandipsangani. My name is Straight Talk John and I will be addressing your queries.
1. You will have to check with your phone manufacturer or old service provider in having your phone unlocked. We do not have any control for this.
2. We only provid 3G at this time.
3. It depends on the BYOP SIM card you have purchased, whether AT&T or T-Mobile. For BYOP programs, this will only work with GSM towers, Sprint is CDMA. In your case, it will work under AT&T towers since you have purchase the AT&T SIM card.
4. Yes, it is a must for you to purchase an Unlimited service or $45 Plan to get service.
5. The APN Settings varies on the SIM card you're using not for phones. Please check your phone's manual or manufacturer in locating your APN setting. When you already have found the settings, here’s how to change your current APN settings:
A. Create a new APN with the following values:
• APN Name: Straight Talk
• APN: att.mvno
• Proxy: proxy.mvno.tracfone.com
• Port: 80
• MMSC: http://mmsc.cingular.com
• MMS Proxy: 188.8.131.52
• MMS Port: 80
B. Delete the current APN from your phone.
C. Reboot the phone.
Hope these helps. Thank you!