MSP430F5324: ACLK and SMCLK shifted to DCO during Noise.

Deepak,
I think your phone will disturb the crystal maybe due to improper layout of the PCB and you see how the fail safe detection is triggered due to a XT2 fault. In this case the automatic fail-safe operatio is triggered and the clock system switch back to DCO. This is described in users guide chapter 5.2.12 UCS Module Fail-Safe Operation:

The crystal oscillator fault bits XT1LFOFFG, XT1HFOFFG, and XT2OFFG are set if the corresponding
crystal oscillator is turned on and not operating properly. After the fault bits are set, they remain set until
reset in software, even if the fault condition no longer exists. If the user clears the fault bits and the fault
condition still exists, the fault bits are automatically set, otherwise they remain cleared.

If a fault is detected for the oscillator sourcing MCLK, MCLK is automatically switched to the DCO for its
clock source (DCOCLKDIV) for all clock sources except XT1 LF mode. If MCLK is sourced from XT1 in LF
mode, an oscillator fault causes MCLK to be automatically switched to the REFO for its clock source
(REFOCLK). This does not change the SELM bit settings. This condition must be handled by user
software.

So please implement fault handling of the OFIFG and the XT2OFFG to switch back to XT2 after the crystal recovered from external noise.
Also please consider the oscillator layout guides described in following Apps Note, it refers to 32 kHz but is true for HF crystals as well.
http://www.ti.com/lit/slaa322