The sound effect itself is likely a generic stock sound or a simple algorithmic sequence. Downloading a 10-second clip for personal use falls under fair use. However, do not try to sell it commercially.
It is technically a Monophonic RTTTL (Ring Tone Text Transfer Language) tone. In technical terms, it resembles the "Old Phone" or "Basic Alert" melody. tmkoc bagha mobile ringtone download
Note: I cannot provide direct hyperlinks here due to platform restrictions, but a quick search on Zedge will yield the result instantly. The sound effect itself is likely a generic
: This is the most reliable source for TMKOC-specific tones. Bagha SMS Tone tmkoc bagha mobile ringtone download