Time limits for assessments by HMRC. From 1 April 2010 the time limits for assessments and claims changed. This also applies to tax repayment claims. All these limits apply from the end of the chargeable period.
A: If the caller is in the United States, Canada or Puerto Rico, the contact number for Xbox Live support is 800-4MY-XBOX (800-469-9269). For an international direct dial call to the United States, the number is 1-425-635-7180.
I do not believe there is a 24/7 support number. You can file a support request via the AWS console and there request to be called. However.. while all the paid support plans are 24/7, the guaranteed response time to a support request depends on your support plan: Features.